Most likely its an ingrown hair. I went for my yearly once and had one, i was worried about it and thats what they said then it went away on its own. they will get sore almost like a pimple because theyre irritated. My didnt hurt as bad as what your saying but it still could very well be a boil, soft cyst, or ingrown hair. Now, if it doesnt go away soon and keeps hurting real bad then id go have your obgyn look at it or skin doctor.
I am having the same problem right now and I have been searching to find the answer but cant. I am in alot of pain when u find some answers please let me know.