Are you sure you didn't take a shot to the stomach and don't remember?
I was playing hoops and got kneed in the gut. A few days later I had blood in my Semen. It lasted a few weeks. (you can imagine my surprise) My sister-in-law played college volleyball where they make you dive for loose balls all the time (the dive and roll drill) she said that during volleyball season she always got blood in her urine.
Everyone might be right about getting checked, however, I'm one of those stubborn people that refuse doctors and I never went and was fine after a couple of weeks.