I'm not going to get into the: "You shouldn't feed live prey animals" thing with you as I too occasionally feed my animals live, t's what they would eat in the wild so why deny them of the hunt completely? You just have to watch them at all times until they make hamburger of the prey. But, this is only IMHO 
As far as the cut, sounds dinky, and you probably have nothing to worry about but sometimes little things like that can run deep. I would take the snake out of his enclosure ad clean it thouroughly with 10:1 water/bleach solution, (rinse til you no longer smell bleach) and use fresh newspaper for substrate til he's healed. For the snake itself let him soak in a 50/50 betadine/water solution for a little while, rinse and dry him off, and apply straight betadine to the wound, making sure it is dry before you put him back his home. Re-apply the betadine once a day for about a week and he should be just fine. If it starts looking worse and he starts acting funny do not hesitate to call your herp vet.
Best of luck to you!
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"Klaatu...Verata...Nicht--cough, cough, cough!"