What did you give him/put on him?
I KNOW that any of the "caine" pain relievers are toxic to chickens-not sure about ducks, just wanted to be VERY cautious with your boy.
Well, I can't find anything about pain relievers and ducks. I bet it won't hurt him. Just try to get something without pain reliever for his next treatment and I think he'll be fine.
You were just trying to help him out-I would've done the same thing.
I would just keep him quiet and warm/clean his wounds and I THINK you can give them aspirin for pain-but that I'm not sure about.
Good luck.
Bummer, did your best. Sounded like a pretty serious injury and that was just what you could see from the outside. There might have been internal trauma and volume shock going on too.