I have a small blue vein on the head of my penis that ends with a small bump. It doesn't hurt and it appeared overnight after trying on tight underwear with an erection. The bump has gone down a little but it's still there. Does this sound like normal blood/vein issues? On first glance, it looks like an STI bump of some kind, but it clearly is a vein that bubbles at the end. I can't see it when my penis is flaccid, but when it's hard the vein feels like a metal pin.