Like many on this thread I had the same symptoms. A smaller sized ulcer on the vaginal area, pain while urinating, swelling lymph nodes. STD test came back negative for everything by HSV1 (which I have had for years from cold sores) but I feared maybe HSV1 had spread to the vulva via oral sex. However, there was only one small sore, it didn't really itch or hurt, and the pin came more from urinating. Also, the itching was more in the vaginal canal. Got to the doctor, and she said that it didn't look like herpes, and the urine test came back negative for UTI. However, there was a TON of bacteria in the area. She said it could be two things: yeast infection or bacteria/staph infection. 

Yeast infections can cause ulcers in localized areas. Untreated, these can become staph (which is what happened to me). She said that she saw smaller bumps, but they were all among hair follicles and most likely due to shaving (I shave there often). Giving me Bactrim for the staph, pain killers for  the pain and another cream for the site. Until you see a doctor, DONT freak out! There are many medical possibilities and abnormalities that must be considered before jumping to the conclusion that it's an STD or STI. Hope this helps.