Butt rash

Lee • Feminist, cosmetologist, and Star Wars enthusiast

I just had sex with my ex last night and I woke up this morning with a small rash on my butt cheeks, nothing on my vagina or anything around that area. Is it possible that its a sweat rash because he was sweating a lot and the friction? It’s not really itchy and it’s just red and irritated. Not sure what I should do? Or if it’s an STD? Help 😩