past 2 days theres been a little yellow pimple like thing under my for skin what could it be?

After i had sex with my gf she kinda teared up my fore skin a little that same say i washed up and and the next day i woke up with this small little pimple like under my fore skin it doesnt hurt, only when i try to like pop it. it is kinda rough and its tiny maybe about 1mm or 2 

heres a pic, any help would be great!

Hello, this seems to be a small friction burn. Make sure she's lubricated(wet) before having rough sex. If it doesnt go away in a week go see a dr