If you know that they didn't bite each others mouths, you don't have to be concerned. If it was just on the head of the snake, it's fine. If you're worried, monitor their mouths. If any swelling occurs, they'll need some medicine to make it all better. I had problems with that, I didn't witness the attack but both of them had a pretty bad mouth infection. I didn't notice the swelling until (probably) a couple weeks after it had happened.