boyfriends penis hurts

I know this isn't directly about women but he's my partner and I'm very concerned, my partner says whenever he gets an erection he feels a strain on the top of his penis when I touch it there's a hard line and he says pulling it down hurts a lot there no fluids nor pain when he isn't hard and he says he feels sore most of the time he should go to the doctor soon but his mom is very suspicious and would wonder why he needs to go to the doctor for that any help while he goes to the doctor?