BigT is doing much better. So much better that he thought he should be able to canter about the commons area to follow LadyZ when I led her around the corner of the barn. Oh brother.
Looking at it closer, it appears to be a puncture wound. The best thing I can do at this point is to get a plastic syringe (or even a Turkey baster) and squirt some iodine solution down the hole to keep it clean.
The puffiness has gone down quite a bit which is good. I had bought some liniment and gave his leg, above and below the wound, a nice rubbing.