Clean the cut. Pick out foreign objects such as bullet fragments. Rinse the wound with the cleanest available water and soap. Didn't pack any? Pry the vodka from your first mate's hands and use it as a disinfectant.
Flatten the barb of a small, sharp, clean fish hook. Cut off the eye and snell the line, which means wrap a knot around the hook to create a flat surface so the line pulls easily through. Or flatten the eye. Straightening the bend also may help.
Run the hook deep so the wound pulls tight. Tie a knot by wrapping the lead end around forceps three times and pulling the far end through the loops. Didn't pack forceps? Adhere to the old fishing saying: If you can't tie a knot, just tie a lot