I had this happen to one of my males also. The sight of it is terrifying. First thing, identify the perpetrator. Second, isolate the injured quail. I didn’t know what to do either. I considered putting it down so it wouldn’t suffer, it decided to wait and see. I did nothing except separate it from the rest and let nature take its course. Eventually to my surprise, it completely healed.
Now. I’m not saying this is what you should do for sure, but it’s what I did.
After everything is said and done you will need to decide what you want to do with the overly aggressive male. Some say cull...
I hope everything turns out ok.