[Jespah]

That's a scary situation for anyone and I'm sure you don't want to have to worry about it happening again, but it may.

Do you always treat Cheyenne as the alpha? She may feel her postiion is threatened by Checkers. Do you feed her before him? You need to treat her as the alpha so she feels secure in her position. I've found with Rupe - he has a bit of an aggressive behavior issue sometimes, that he'll challenge a female that he doesn't know well, maybe a couple of times and if she gives it right back to him, he'll soon decide it's not worth it and stop the challenging. He has a new friend who he runs up to and licks and goes crazy all over then once and a while the two of them go at it like they're going to kill each other. It's all mouthing - but Rupe did a couple of nicks in his ear. We just watch them and try to be calm enough to let them sort it out.
Even though you should treat Cheyenne as the alpha, Michael is right - even when she lifts her lip at him - tell her no. Any behavior like that must be nipped in the bud.
Good luck!