Slight pain in the male organ for some reason.

So to start, i'm a 20 year old male and I've mastubatived at least once a day.

For the past couple of days there's been a pain at the tip of my penis, the head I think its called.  The pain isn't consistent, sometimes its there, sometimes it isn't.

There isn't any redness or swelling, and it mostly only hurts when I'm erect.

And the pain isn't even all that bad, maybe 1, 2 if I'm feeling generous. Its there, but it dosen't really bother me all that much.  I guess the best I describe it is that it feels like there's a bruise on there that I somehow keep touching.  In fact, that's what I thought it was except that I couldn't find any dark spots down there.