What Was The Small Red Rash On My Boyfriend's Penis?

ok so me and my boyfriend just has unprotected sex for the first time for both of us. he did not cum inside of me. but im worried. he said that he has a small red rash like dot on the head of his penis. he said he only gets it when he jacks off or when we had sex. i looked up some answers and it said it was a friction rash, but im still scared its something else. should i be scared? could this be an STD? can i get something? help.