So, I recently got a big mixed goose and a Chinese. They have been doing great, and I'm now totally in love with geese. About a week ago I noticed the white on had a black thing on his beak. I caught him today and realized it looked more like a wound or like it was rotting away. I feel so bad I didn't check him right away. He is acting normal, chasing the dogs and eating and drinking. Can anyone tell me what it is and what I can do?