What's that between your legs? Do you have skin bumps, blisters, or sores in your pubic area, on your genitals, around your anus, or on your upper thighs? You need to know what's going on!
Here's an overview of causes of skin lesions in the groin area.
Folliculitis And Boils
The name folliculitis pretty much speaks for itself — the tissues that hold your hair in place are called follicles, and "-itis" means "inflammation". Folliculitis occurs when a hair follicle becomes, or often a whole bunch of hair follicles become, damaged or blocked. They then become infected, usually with Staph.
- Wearing tight and/or synthetic clothing — the friction causes damage.
- Improper shaving techniques, such as shaving too quickly, shaving without using shaving gel, or using blunt, old razors.
Also called Barber's itch or razor bumps, folliculitis isn't anything to worry about. You do, however, need to keep the area clean, wear loose cotton undies, you can use hot compresses to ease your discomfort and promote healing, and you should see a doctor if your folliculitis doesn't go away after a few days or if it keeps coming back. In this case, antibiotics or antifungals can help you out. 
Boils are bigger than razor bumps, and also more painful. Characterized by a volcano-shaped bump with a yellow, pus-filled, center, boils can easily grow to a size of two inches or more and generally take around two weeks to begin draining if you do not seek medical attention. 
If you're dealing with boils on your buttocks or genital area, the best thing to do is to:
- Avoid touching the area too much, and especially avoid attempting to drain the boil yourself.
- Use warm, moist compresses on the boil a few times a day.
- Keep the boil clean with antiseptic soap.
- Use sterile dressings on a boil once it bursts — boils are contagious.
- If you develop a fever, are in great discomfort, or your boils keep coming back, see a doctor. Antibiotics are often used in these cases. 
Genital Skin Lesions Caused By Sexually Transmitted Diseases
Since an estimated 90 percent of US adults will have come into contact with Herpes Simplex 1, the virus that causes oral cold sores , I fully assume that you have a very good idea what herpes looks like.
After you first become infected, you may also notice fever, a general achy feeling all over your body, headaches, and swollen lymph nodes.  Note that, while intercourse-acquired genital herpes cases are generally HSV-2, the HSV-1 virus can show up in the genital area too, after receiving oral sex from someone with HSV-1 .
There may be one or many, they may appear anywhere in the genital area, and they may be small or grow very large. Larger genital warts are often described as looking somewhat like cauliflowers. There is no pus involved, and genital warts do not look like pimples. Note that HPV is also associated with various cancers, but the type that causes genital warts isn't known for this. Genital warts may disappear spontaneously, or they can be frozen, burned off, or surgically removed. 
All stages of the disease involved skin lesions of some kind:
- Primary Stage: You'll usually have one sore where syphilis first entered your body, though there many be multiple sores. These are called chancres, and they are typically round, painless, and firm. The initial chancre(s) take up to six weeks to heal, regardless of whether you receive treatment. (Note that the initial site of infection may be somewhere where you wouldn't notice the appearance of the sore, such as inside the vagina.)
- Secondary Stage: You may notice a skin rash on various parts of your body, along with lesions of the mucus membranes — such as inside your mouth.
- Latent Stage: No symptoms occur during this stage, but the disease is still present. This stage can last for years.
- Tertiary Stage: This is where the true ugliness of syphilis reveals itself, in the form of organ failure and even death. It doesn't strike everyone infected with syphilis who did not seek treatment, but it can happen. Because antibiotics can get rid of syphilis quite easily in its early stage, seeing a doctor as soon as you notice symptoms — or even better, having regular STD testing if you are sexually active — is very important. 
Skin Conditions That Can Lead To Genital Lesions
Eczema, characterized by dry, itchy and flaky skin that can cause oozing when scratched, can indeed appear on the genital area in both men and women. [10, 11] Contact dermatitis, caused by contact with irritants such as harsh soaps, laundry detergents, or female hygiene products, is more likely, however — and again, both men and women may be affected. In this case, you may notice itching, welts, and redness.  Corticosteroids benefit people with both these conditions. Keeping the skin moisturized is very important in eczema cases, while antihistamines and removing the irritant best serve those with contact dermatitis.
Jock Itch is a fungal infection that leads to a typically round skin rash along with itching and redness. Also called tinea cruris, it's more common in people who sweat a lot (like avid athletes — hence the name), and it's treated with antifungal medications. Keeping your groin dry also helps speed up healing. 
Psoriasis, a chronic but non-contagious skin disease resulting from excessively rapid skin cell turnover, causes slightly raised, red, scaly patches of skin that can be very extensive . When it affects the genital area — including the pubic area, the genitals themselves, the anus, the buttock crease, and the upper thighs — it can lead to severe distress and greatly impact your sex life . Corticosteroids. moisturizers your doctor recommends, and UV light treatment are the best treatments for genital psoriasis .
Molluscum contagiosum, which manifests as tiny, raised, and red bumps on the skin, is a viral infection. The genitals are merely one possible location of these bumps, which can appear all over the body. Contagious while active, it can be sexually transmitted by those people who have active genital lesions even though it is not considered an STD. The condition can also be spread in gyms, during contact sports, or by sharing towels or bed sheets.  Molluscum contagiosum eventually clears up on its own and requires no treatment.
I Still Don't Know What I Have: What Now?
Are you quite sure you have folliculitis, or even a boil? There's usually no need to see a doctor. Contact dermatitis also doesn't necessarily require medical assistance. If you are really not sure what you're dealing with, however, you have a different story on your hands.
Looking for pictures of conditions that sound like possible candidates might help you get closer to an answer, but let's face it — self-diagnoses can be wrong, and you don't want to treat the wrong condition with home remedies or over the counter medications, because that gets you no closer to being rid of whatever is plaguing you.