Well, you could visit him, buy/make him a get well soon gift, make him a get well soon card, comfort him, talk to a trusted adult or get his classmates/friends to sign a card for him.
If you play Minecraft, you could also just build dinosaurs in Minecraft. (This one is a joke)
Sorry if the last one offended you, I just wanted to make you laugh at least a little.
I hope your friend feels/gets better very soon.
-Minecraftnerd