Did I do the Right Thing for my Horse's Wound?

If the wound is so tiny, but deep, and she's that swollen it sounds like more of a puncture wound, which can cause a lot of pain, and also can open her up for infection. It sounds like you're on top of it pretty well, although I wouldn't make any umptions as to whether it's soft tissue damage or a fracture, or a foreign body, just off of the way she limps. It may take X-rays or flouroscopy to see what's going on inside there. I agree with the other poster about the tet booster, and I think you may also want to consider giving her antibiotics for a few days. A little Lasix can also work wonders when it comes to taking fluid out of tissues. I've had the best luck on wounds like that with a DMSO/Furacin sweat. It will be hard to do if you aren't able to wrap the knee, but if you just paint the whole leg from several inches above the top of the swelling on the knee, down to the ankle and then wrap several layers of plastic cling wrap over the whole length of the leg, and put a standing wrap on her lower leg with 1 layer of duct tape around the top of the plastic, it should hold up overnight. The swelling should be drastically reduced by the time you take it off to hose it the next day, although it may fill back up again after being left open for a few hours. If it's not a lot better within a few days you should have a vet check it out. Another idea is Nolvasan ointment, which is really effective for wounds, but again, you would need a dressing to keep it on, and it wouldn't have the anti-inflammatory effect of the DMSO. Whatever you do, I wouldn't try to close it up right away. You want an injury like this to remain open and draining until all danger of infection has ped.