Ugh I hate when this happens. Heel, pastern cuts are obnoxious to take care of. When Jake split his heel he was out of work for three weeks. Now this really depends on where the cut itself is. Because that area of the horse moves so much, sometimes you have to worry about it opening up again, and having a hard time healing. With my horse I had to wait until it was healed before I could ride, because if he started to stretch out it would re-open. With a riders weight upon their back their joints tend to flex a little bit more than without, causing the skin to stretch a little bit more. So it depends, I have shown with cuts that were small and in places where they would not stretch over a joint. Let your horse tell you too, if he seems uncomfortable or is acting a little off, I wouldn't either.