As it is close to the eye all you can do is just keep an eye on it .If need be to keep clean you can just use something like a q-tip with warm salt water on it but be careful not to get in the eye If it is a deep wound or keeps bleeding or starts to smell of look funny then you need to take him to the vet as it will mean infection . I wouldn't seperate from the others unless he is getting bullies as they are much happier with others.

My 4 week old Pekin duck has a small cut under his eye that had been bleeding. It doesn't look like it's bleeding at the moment, however. How should I treat the cut and will I have to separate him from the other 5 ducks?