What Can Cause Pain In Penis In Kids?

My son is 5 and today started complaining about his penis hurting. I checked him and it was swollen as well about halfway up the shaft. I took him to the dr and they sent me to the ER the ER said that it is bruised. He is now crying in pain because he says it hurts really bad. Is there anything I can do to help relieve the pain for him, he had ibprofin around 4pm today.