Sounds like your dog's eye may have been scratched or punctured. You'll need to see your vet as without proper treatment they become infected and your dog's eye may need to be removed or without that they can pop out or explode. Usually if seen soon enough you just need some antibiotic drops or cream and monitoring by the vet.
Oh my goodness, with puss as well. You better get your dog to a vet, this sounds a lot like infection. As well, do you know who he got in fight with, because this animal needs to be reported and observed for distemper or worse rabbies. Try to get to a vet, try a warm compress, use a bowl a warm to hot water and add a tsp of salt to clean. Maybe if you can patch it up as well, would not make matters worse. Good luck to you and your dog. Dang, I hate dog fights or any kind of fight for that matter