Penile bruising is an unpleasant phenomenon that can be alarming for males. A bruise on the penis could signify a number of different possible underlying diseases or pathologies so you need to make sure you are informed and take the necessary next steps to seek treatment. Here, I will present 6 possible causes of penile bruising and what immediate steps you must take next in order to deal with the problem because it gets much worse.
Blunt Force Trauma
At some point in every male's life, you will be able to recall an unpleasant experience of having some type of blunt force trauma to your genitalia. Whether playing sports, accidentally bumping into furniture or by just bad luck, it is something that can leave a lasting impression even if these events can be few and far between. An unfortunate fact about male anatomy is that the penis is a very sensitive organ that has many superficial blood vessels. This is a great advantage during sexual intercourse to help male achieve and sustain erections but any type of micro-trauma to this region can lead to burst capillaries that can be seen as bruising on the penis . Most damage that can come from these types of injuries are seen in the scrotum but if you find yourself on the bad end of an accidental kick or tackle, you need to have a medical evaluation to make sure your testicles are unharmed and then should recover after conservative treatment. Never underestimate the importance of the jock-strap. 
Another potential route of penile bruising can be more self-induced. Another painful memory that most of the male population can relate to is the accidental trauma you may self-inflict when you are using zippers. Urinals are great to quickly relieve ourselves when Nature calls but when you become lackadaisical, there is a good chance that you can accidentally tag some of your foreskin when unzipping and zipping up your jeans. This will almost always cause a bruise on the penis to form because of a large amount of pressure localized to a small area. If you find yourself in this situation (hopefully not while reading this article), you can try to gently separate the metal teeth from your skin but if it does not come away easily, you should go to the Emergency Department where they can apply topical anesthesia and cut away the zipper to minimize damage. 
Side Effects of Medication
Sometimes superficial penile bruising is a small price to pay for bigger ambitions. Patients suffering from erectile dysfunction normally use Viagra tablets as a medical remedy to achieve an erection to have a better sexual intercourse experience but some of the few contraindications of Viagra can make this pill not appropriate for everyone. Some of the more common contraindications are prior heart attacks, liver disease, and blood pressure medications containing nitrates . This population can use an alternative method of enhancing erectile function by using direct injections into their penis in order to achieve the same erections .
Another potential reason that patients could also see bruising after injections would be when patients attempt to increase the girth or size of their penis using hyaluronic acid. This is not a procedure that doctors will recommend to patients for any reason but due to the number of supplements you can buy now-a-days on the Internet, it is something you should be aware of if you try this for yourself. 
Another condition that can lead to a bruise on the penis would be any type of trauma that occurs to the penis when it is erect. Penile fractures or other types of blunt force trauma to the penis during times of erection can lead to blood vessels easily rupturing and patients will often present with severe bruising and swelling on their scrotum as well as their penises.  This is a medical emergency and you need to get urgent medical attention as quickly as possible to restore blood flow properly to the penis .
If you haven't picked up on a pattern seeing a lot of the previous causes were mostly self-caused, this next one should make it pretty obvious at this point. Males who frequently masturbate are able to cause a lot of potential trauma to the soft tissue of the penis if they use too much force. Reducing the frequency and intensity of masturbation episodes can help prevent any penile bruising. 
The last field worth exploring that could ultimately lead to bruising on the penis could come from operations that a patient recently had. Patients having any operation will most likely be given medications like heparin or coumadin to prevent clots but that also makes patients vulnerable to bleeding. This only magnifies the risk of all previous 5 cases of bruising on the penis.  Studies show recent vasectomies or other operations around the penis can also easily predispose patients to have penile bruising.  These will generally self-resolve in a few weeks after the operation.