Pimple-like bump

About 5 days ago I noticed a pimple-like bump about three quarters of an inch away from the head on the shaft of my penis.  The bump grew over the following two days, like a pimple would, and eventually formed a puss center.  I immediately thought this could be herpes because I had had sex with a girl about a month before this.  It was unprotected for about 10 seconds.  The area did hurt for a good three days when it brushed up against my clothing.
About two days ago, the bump popped in the shower without me really putting pressure on it and started to bleed.  It wasn't a lot of blood and like I said, similar to a pimple.  Since then, the area has started to heal.  No more pain, and it looks like more of a tiny dried up scab now where it once was bleeding.  I am aware that it's possible to get pimples on the penis, but was wondering what I should do.  I'm thinking the best thing is to just go ahead and get a blood test anyway and in that case, would I need a doctor's prescription?  Should I be concerned?  

[slacker101]

Sounds like a pimple