My brother fell out of our tree fort and hurt his shoulder. Advice?

My actual brother is a big jerk. He was smoking weed and poking fun at me and my stepbrother. My stepbrother got mad because Derek (my real brother) was taunting us. Finally Dale (my stepbrother), got so angry at Derek that he kicked him in the head and Derek fell out of our tree fort and he hurt his shoulder. Despite him being a jerk, I feel like I should help my actual brother get some treatment for his shoulder pain. Do you have any advice for me to give my brother Derek for treating his shoulder pain?