Help! Something wrong with beardies tail!

I was over at a clients house where she was showing me her bearded dragon when I noticed its tail was damaged. My client is mentally disabled but takes great care of her dragon and has help to take care of him. I asked her about him and she said she bought him from the petstore like that and they said it was fine.

I used to have a bearded dragon myself and know it's not ok. I think the petstore intentionally sold her a sick animal because they know she is disabled. Any clue what is happening to his tail or any advice for how to help care for it. There are no exotic vets in the area so it's unlikely we will be able to get vet care for some time