That is great to hear. Watch him carefully when he goes back into the flock. Let them free range together for times when you can watch for pecking. Perhaps keep him in a cage for a few days inside the coop so they can be near him before they get together. Good luck.
Yes you can use saline or salt water (1 tsp to 1 Quart water boiled for 15 minutes, then cooled,) hydrogen peroxide, then rinse, or just soap and water. Do you have plain neosporin or any type of antibiotic ointment? Coconut oil might be a good substitute. Do you mean that his beak is cracked...
Do you have some Vetericyn wound spray, Betadine, or Chlorhexidene that you could use to clean his wound. Vetericyn is the easiest just to spray on. The other two should be used according to label with water. Then you can apply some plain antibiotic ointment such as Neosproirin or Bacitracin...