Google molluscum contagiosum, and see if that's what you have. If you think that's what it is, you should see a doctor to get it confirmed. There are treatments for them, though some opt to leave them alone since the treatments may cause scarring. Talk it over with your doctor.
This is a sexually transmitted disease, but can also be acquired from sharing gym equipment, etc. It's spread around day cares quite frequently. Given that it's on your penis, though, I'd guess it's from sex.
If it is MC, it will go away - it's not a lifetime thing. It could take some time for that, though, and it's highly contagious. You should avoid sex while you have symptoms. The incubation period for this can be a few weeks up to several months, so if you've had multiple partners in that time, it may be impossible to know how you got it. You should also talk to your most recent sex partners, if that's possible, going back maybe 3 months or so.