A vertical nipple might actually work well, but not the horizontal ones, he could tap the pin with that bottom beak and water would run right into his mouth.Personally, I think nipple watering would be hard for him to navigate. He would have to peck it in order to get any water - he only has a bottom beak, so I am unsure how he would peck and catch water at the same time.
Very odd situation.
As there was no bleeding, unless I missed that part, I wouldn't treat it like a wound.
Wonder of there was some kind of injury that caused the beak to crack and 'die' then break off?
Sure hope it grows back, but I've got my doubt.