This is kind of a loaded question because bumps on a man’s penis can be due to a variety of things—ingrown hairs, pimples (yep, a man can have pimples on his penis), an allergic reaction to soap or detergent or it could be an STD (like genital herpes or HPV).
That said, probably the better questions to ask are
1. Has he always had bumps on his penis (or in his genital region, period)?
2. Have the bumps recently changed in size?
3. Is there any discharge coming out of the bumps?
The first question, you’re only going to find out the answer if you ask him directly. But if the two of you are engaging in sexual activity, there’s no reason to be shy about bringing it up (just make sure you’re asking in a way that doesn’t make him feel self-conscious because how would you feel if he asked you the same thing?).
As far as the other two questions are concerned, well, it’s never a great thing if bumps change size or there is discharge coming out of them (, there are exceptions, of course, especially if it’s a zit). At the same time, you don’t want to ignore the elephant — err, big oozing bump — in the room because if he does have an STI or STD, it could be contagious whether you have sex vaginally, anally or orally.
Bottom line: If his bump is a big enough issue that it bothers you, bring it up to him. If it has always been there, while he might be a little uncomfortable talking about it, what he shouldn’t get is defensive. If he does…put sex on pause and also mention that you both should probably see a doctor.
Just to make sure if the bump, or bumps, are truly normal or not.