3 hours later is not going to be STD related. But since I has cheated I can see your position and thinking.
i know i feel bad my guy called me and was crying but hes cheated in the past so i am lost and upset as well as stressed out we were having sorta rough sex and then about 3 hours i have a lump or bump whatever it is its freaking me out
Bumps can be many things often not a STD, but you would have to see a Dr for proper diagnosis. Just seeing a single bump is not bounds to think someone cheated.