You should be using ice, not heat, at this time. It takes a few days for the swelling to decrease. Motrin can be used for pain and headaches, but it will not heal the bruise itself. That is a matter of time and the body s efficiency at healing itself, which is usually pretty good in children. Keep a close eye on him the next couple of days to be sure he doesn t develop any symptoms suggesting a more serious injury. He should be seen at emergency if he develops excessive sleeping, severe vomiting, change in personality, weakness or numbness on one side of the body, severe persistent headache, difference in size of the pupils, anything that looks like a stroke. These could indicate that the injury has affected the brain. Most kids do well with injuries like this and feel better within a day or two. The swelling should go down fast but the bruising color itself may take a week or so to go away. Hope this helps.