What Causes Penis Pain With Irritation, Swelling And Bruising After Intercourse?

Hi i was having intercourse with my girlfriend last night. after a bout 5-10 minutes i started feeling a pain in my penis. It was not an imense pain, more like an irritation. on examination, (still erect) my penis had become swollen, and a little bruised. I didn't think much of it and went to sleep. I woke up this morning, my penis if bruised all over and is still swollen. It doesn't hurt, and my urinating is as normal. im a little worried.