It may be an in grown hair. I had one that size before! Hurts like heck!!!! But idk, ask the doc about it!
Yea it sounds like an in grown hair I had two they where infected doc had to drain them b sure u show doc if they r that big n hurt may need antibiotics
Or it could be a pimple lol i get acne down there sometimes... it looks different than acne on your face, I'm 100percent clean too. So acne or ingrown hair.
It could be a bartholins gland cyst. If so it will get worse and more painful till you can't walk unless you go to dr.