Bag Balm is very good for saddle sores, all kinds of abrasions really..,. Also, if its really tender, you could try some Mole Skin (sp?) from Dr. Schols I believe. Its a rectangular sheet of a kind of padded dense felt on sticky back paper. You cut out a piece big enough to overlap the sore spot, then cut out the center area, that would go over the sore.
So,..you have a built up rim around the sore that will take most of the pressure and rubbing away from the abrasion/saddle sore .