Hello,
I discovered this sort of rash/burn on my penis It has discolored my penis shaft and looks like a few layers has come off but I am not sure. I discovered this about a week after i had sex with a woman. I used a condom but my penis did go inside of her without a condom for a second. The day before this appeared I did masturbate vigorously. I am not sure whether this is an std or a friction burn. Please help. 
Because you experience a discolored skin rash and burning sensation, I suspect you have jock itch, a common type of fungal infections. Usually, it goes along with dryness, itching, and peeling or flaking skin. If you experience those symptoms as well, see a doctor for official diagnosis.
There is no pain while urinating and have not noticed any discharge. It has been two weeks since the sexual intercourse. 