I have a small pimple on the underside of my penis. I t does not hurt or anything. I t is just something I thing should not be there. What could have caused it?

Could just be an ingrown hair, could be something else. If it doesn't go away, see a doctor.

Probably the same thing that causes other pimples. If it doesn't hurt then don't worry about it, it'll go away on its own in several days. Did you have sex recently and are concerned that you've contracted an STD? If so, be on the lookout for other symptoms. A common pimple, in and of itself, is not a typical symptom of an STD. If other symptoms appear as well, then take notice. Above all, do NOT have sex without a condom until the pimple heals, even if you don't suspect an STD as it'd be very easy to contract something while the pimple is present.

Haha well you should help people if you can. Like she said yeah it could just be a pimple, I think it may be an ingrown hair, if it goes away, nothing to really worry about, if it gets worse see a doctor.

Stress. Hygine... get a bar of soap and scrub.. take at least 2 showers each day... and keep changing your underwear... itsll come off do not pop it!!