Legal Question in Personal Injury in California

In playing any sport, you assume the risk of common actions that can be anticipated. So the facts of how your nose was broken determines if you can sue anyone.

If you broke it as part of the game, of course you can't sue. That is one of the risks of a flag football game; you can't sue for risks you voluntarily take on. If they got in a fight with you an punched you, or hit you outside the scope of the game, then maybe, maybe not, depending on the details.