Your description covers a lot of possibilities but I'm assuming if it was a pimple you wouldn't be so concerned. If it's more than that, check out "Bartholin's cyst" on Google images to see if that might be what you have. If it is, you can find treatment options on the Web. Good luck.
Do you ever shave your pubic hair or bikini line? It could be as simple as razor burn. Or, if you don't have the greatest hygiene, it could be the adult equivalent to diaper rash? Try some hydrocortisone cream (Cortaid, Cortizone 10) if it is rash-like at all. Hope that helps!
Have you ever shaved that area? If you have it could be a nasty ingrown hair (It could be this if you didn't shaved though). If it's white and looks like a white head pimple, you could poke it open carefully with a steryl needle and let the puss out, and see if any hair comes with it. If it is just dark or red leave it alone, as it could also be a boil, and it will go away much faster if you leave it alone.