Let the punishment fit the crime

So I have a rule in my house - no fighting. I'm sure that's a common rule. Generally if there's a fight between the girls, I give them a warning to stop the fight and find a solution. Sometimes this actually works! Well the other day my usual warning was no good. Perhaps it was because I was on the phone trying to have a conversation with my brother like a normal human being. Silly me! So anyways, the girls were going at it over something and eventually, while I was getting off the phone, Libby was hitting Nina on the head and Nina was biting Libby's hand. I sat them both at the kitchen table with ice packs and tissues and Libby says, "are we in a timeout?" I just laughed and asked her, "does your hand hurt?" and she of course said yes. and I asked Nina, does your head hurt? and she said yes. And I said, "well then you've punished yourselves enough." Fighting sucks doesn't it?