I have had an ingrown hair in the groin area, went to doc, treated with antibiotic, went away fine. Then a few weeks later had a blister form on the outside of the vaginal area and it was one spot that became huge (size of a large pea), never had other symptoms (nothing internal wrong it seems) but then eventually ruptured and is now going away on its own(using ointments, keeping clean, etc...). The question is, is this an ingrown hair or what. I do triathlons, was biking many miles a week in tight fitting, damp shorts and competing in these races all summer. The blister appeared after a particularly grinding week of biking, getting ready for race. Then, did race and really that was when it got bad and got huge. Is this from rubbing on bike or could this be an STD. Engage in oral sex, regular sex with a partner who has no known problems- so I think.