here's an answer from another site:

Date: 3/22/2004 3:56:13 AM
Subject: Spots - Perhaps Petechiae?
Name: Kid

While I whol heartedly concur that the best source of advice on this subject is to promptly consult a urologist, one possibility is something called "petechiae".

The only time I had them (and that was only for a day or two) was when I first started using a VED - vacuum pump for the penis. Too much pumping, the instruction manual explained, could result in petechiae (little red dots) appearing on the surface of the penile skin. My understanding was that they were the result of very tiny blood vessels being aggravated or popped, resulting in tiny, pencil point size dots. They were harmless, but nonetheless, a visual indicator of what was happening below the surface.

By any chance were using a VED or "over-using" your penis in some way?

Get thee to a doctor.