Soaking in epsom salts daily can help with pain and swelling. But like any bad sprain or strain, or bruising from trauma, mostly it's time to heal that's needed. The more you can get him to rest it the better. Being a chicken, he's going to do what he's going to do, the pain will help to get him to self limit himself some. Even if you just crate him for periods during the day, it can help.