UPDATE: here's what it looked like on May 7th, when i first noticed something weird was going on: https://imgur.com/a/9rujFdw
Have you ever had sex - like oral sex, vaginal or anal sex?
If you haven't, you don't need to worry about it being an STD.
Other things can be really dry skin, eczema, psoriasis, yeast or another fungal infection - it's a long list. Your best bet would be to let a doctor see it, maybe get it cultured and go from there.
forgot to mention. it only hurts when i touch the affected area.