That is extremely hard to diagnose over the internet like this. It could simply be a pimple or it could be something such as herpes, depending on your sexual history. You'll have to go see a gyno, regardless of their gender, to know for sure.
It can be anything from an std to a pimple. You should have it looked at, but usually for an accurate diagnosis you need to have it cultured within the first 24 hours of it's appearance. Find yourself a doctor now, male or female. This way you will have somebody to turn to with your questions/concerns. Good luck.