Thank you for getting back to me. I think your temperatures are fine. Leopard geckos do best with a temperature gradient of 82*F on the cool side to 88*F on the warm side. However, I have another concern, and that is the heat rock. They are horrible for lizards. Lizards do not have very good heat sensors on their undersides. That means even if the heated rock is maintaining the temperature it is set on, burns can result. The lizard simply doesn't know when its underside has become too hot. Sometimes a lizard can go for years without a problem, but often it's only a matter of time before a burn occurs. A burn would cause the skin to blister on the part of the body that was on the rock too long. It's possible she leaned up against the side of the rock Pet stores recommend these rocks, and at first glance they seem like a good idea. Pet store staff get their information from literature put out by the manufacturers of heated rocks. Here is a nonprofit site where you can read the truth:http://www.anapsid.org/hotrock.html
Also, take a look at this video:
Since the injury is on her back, it doesn't seem very likely the rock is to blame, but I would get rid of it before something does happen.
I suspect we aren't going to find the cause of the injury, but I can give you first aid for it. Start with a special soak. Buy Pedialyte (yes, the kind for human infants). Prepare a shallow bath consisting of 1/2 water and 1/2 Pedialyte. Soak your gecko for about 20 to 30 minutes twice a day. Reptiles can absorb the electrolytes and fluids through their vents (where droppings pass out), so make the water deep enough to cover the vent. Be sure to supervise closely. This measure will help with the dehydration that has occurred and may improve her appetite.
Next, get some Betadine (povo-iodine solution). This is sold in pharmacies in the first aid department. Clean the affected area with it. Follow that with a light coat of plain Neosporin. The Neosporin can be repeated twice per day.
If these measures don't help in a couple of days, or if the wounded area starts oozing or swells before that, it would be best to see a reptile vet. There may be infection that requires prescription medications. This link will take you to a directory of Canadian reptile vets:http://www.triciaswaterdragon.com/canrepvt.htm
If you have more questions, let me know by clicking on REPLY. I hope your gecko will quickly heal.
My goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back, I am happy to address follow-up questions. Please remember to rate my service only after you have all the information you need. Thank you!