Eye missing looks infected!!!!

Hi so about two weeks ago I sold a guy this gorgeous rooster (I own a small chicken ranch) and today he brought it back and said its eye was missing I didn't take a close look at him until the guy left. the rooster a Swedish flower is indeed missing a eye but it's all puffy and he has lost weight from when I last held him his brother one that I kept definitely was more weight to him please please help i don't know what I should do I have given him plenty of food and water is there anything pacific I should give him or any medication?