Julie here is some ER advice, hope it helps . . .

If he has seizures I would be on the lookout to make sure the bump didn't decrease his seizure threshold. Ice to the owie on the head and be on the lookout for severe vomiting, headache, changes in vision, hard to wake him up, etc. . . The bruise will be ugly and ice will help, but it will have to go away on its own. If he keeps having severe pain in that leg make sure that he hasn't injured the bone. Otherwise you can give him tylenol or motrin for the pain (if he is not allergic- and it doesn't go against any other meds).