This happened to my resistor after I tomahawked it into a massive rock hillside. I was so bummed, put it back in the bag and after a hole to cool down and collect myself from the sadness, I heated it up with my lighter and formed it back together. I hardly notice it now and flies exactly the same as it did before the trauma. If this were to happen again I would wait till I got back home and heat up a thin piece of metal, maybe a knife or file or ruler and get the inside of the cut first and form it back together. Then heat the outside if necessary. Mine is holding fine after a couple weeks just by heating the outside, but I would feel better knowing the inside was good and fused as well.