I (foolishly) jumped in the middle of a one hit bar fight and stopped the guy from hitting again-the one guy was out on his feet-I could see the hit guys eyes glaze over and roll back into his head -so I jumped in when the guy started to hit him again and I blocked his arm. The guy that got hit fell down in slow motion and knocked over a stack of empty beer cases...he spent 3 days in hospital from one blow to head. If he had been hit again its possible he might not have survived. the guy that got hit was drunk and started it...
Sounds like you did the right thing to me.
Of course, you didn't mention what happened to you but kudos for stepping up. Sometimes even if you get hurt, if you were doing it for the right reasons, it's worth it.