I have a fairly large red bump midway up the shaft of my penis on the left side. I noticed it a few days ago, and until today had decreased in size. Now it is about the size of a bb, and hurts when touched. I had a bump similar to this about a month ago, but it went away after the course of a few days. I'm 16, and a virgin. Also for a while it has stung while urinating, but I don't think that is related to the problem.

Let a doctor have a look at it. Then you will have the expertise of a professional to go on.

I'm going to assume that you're telling the truth when you say you're a virgin.

If this is the case, there's a good chance it's just a simple irritation due to new clothes, soap, weather, etc. It could also be an irritation caused by masturbation.

i have a fairly large red bump midway up the shaft of my penis on the left side. I noticed it a few days ago, and until today had decreased in size. Now it is about the size of a bb, and hurts when touched. i had a bump similar to this about a month ago, but it went away after the course of a few days. I'm 16, and a virgin. also for a while it has stung while urinating, but i don't think that is related to the problem.
Why in the hell would you talk about your penis to everyone in the world!

It is more than likely just a simple cyst caused by irritation or genetics. But if it hurts and is not going away, see a doctor and get a professional opinion and treatment.