“Spots reappearing on penis.”

Hello! My problem is that I keep on getting a random spot every now and then on the shaft of my penis. I believe they are ingrown hairs (My best guess, I could be wrong) and they vanish after a few days with no harm done until another one appears in a month or two. The things I'd like to ask are why do I keep getting them? And is there a way to reduce/stop it from happening? I would like to add that I'm still a teenager so I'm unsure if any body growth has any relation.

Thank you for helping out!