Even if it is a disease instead of a wound, there is nothing that you can do about it. Just let it be and hope for the best. Treatment would require removing it from the tank and then guessing at what it is for medication which probably won't work in a tank with sand anyway - all of this could be more deadly than the hole.
Just keep it well fed with high quality food and that is about the best that you can do. If she is eating, then that is a great sign.