Zit like bumps on penis.?

I have had three zit like bumps on my penis, all on the underside of the shaft over the last three years. These bumps will not pop without a needle or puncturing them. How worried should I be. I have had no other symptoms of any kind. They all have disappeared once they are popped/punctured and have all been random, none right after the other or of any kind of pattern.

?2012-10-09T04:28:34Z

Fordyce's spots perhaps.

Very common.

M