Bruising on my scrotum and base of penis?!...

Hey guys, I have no idea how but I felt tender downstairs and had a look and there was a slight discoloration of my scrotum, a light yellowish brown, barely noticeable. (from my view it's to the left of my penis about a cm, on my scrotum, aboutthe size of a 5¢ piece, and then from the base of my penis down the centre of my scrotum to the bottom of it. .)

This was Monday morning, last time I had sex before then was the early hours of Sunday morning and I did feel a slight discomfort on my pubic bone right behind where the 5¢ bruise is.

It's now Thursday and the 5¢ size bruise is completely purple, like a deep purple nearly black, and the one down the centre of my scrotum is the same?... I have no idea what I've done; my testicles aren't sore on their own, I can rub and squeeze them without discomfort. However beneath the skin of the 5¢ bruise is tender and hurts and I can notice it every now and then without touching it.

Please help?