First thing is to get it off the sand. Get it in a sterile environment. i am dealing with a similar rescue at the moment. Someone decided to yank the shed off a Sinaloan Milk's tail.
(pics taken by JuliusSqueezer at www.reptilehaven.net
Cleaned the wound. Constant neosporin, raw tupperware enclosure with newspaper substrate and a hide. A regiment of Baytril. That was what I did. He has improved a little, but he main thing is that he has not gotten worse and he has eaten for me. He is in the blue right now so we will see how that goes.
It just goes to show you that a rodent can do alot of damage really quickly. I am however irritated that you knew you should be whacking them and you didn't. Particularly when feeding two. That takes alot out of a snake. But I digress. You sought help, even if it was after the fact, and are trying to do what is best for the snake. Mistakes happen. So be it. There are enough threads about the evils of live food where many a herper has been chastized. I think I am safe in assuming that from now on you will be feeding dead preay and preaching the gospel of it to other keepers. Good luck with the little sand sniffer