Pics would be good, but it sounds like sulcus thrush. Air kills it, so it needs to be kept clean and open to air. Soak the hoof in warm water with some epsom salt or iodine, and then stuff the hole with some cotton balls to keep it open to air. There's a pencillin called Dry Cow that will work on killing it from the inside out. Squirt it in there every other day until the frog grows back in from the inside. This is all assuming that it is, in fact, deep sulcus thrush.
You just have to see your distance...you don't have to like it.