Just chiming in to say I agree with the previous posts. Keep it damp, damp paper towels for now, and an emergency vet visit tomorrow AM. Make sure the vet is aware that this is an emergency, and they should bump a routine visit for you. Even if it does look better tomorrow the gecko needs to see a vet.
I agree that the bark chip substrate isn't the best choice, but that's something that can be addressed after the medical situation is resolved.