Ok So My Buddy He's To Embarrassed To Ask His

Ok so my buddy he's to embarrassed to ask his doctor I disagree but everytime he goes over a hill in the road when we're driving around his penis hurts and it's happened from what he told me for going on 13 years now I don't get it because when we go over the hill at the same time my junk doesn't hurt but his does he has never had sex or anything remotely like that so I know it's not an std I'm just concerned for my friend is all