Chinchilla biting tail stump

My rescue chinchilla Wilson won't stop chewing his tail stump and I'm running out of ideas what to do. I've had him several months now and he came with his tail amputated as he got in a fight with another chinny which severely damaged his tail. It had all healed nicely but the last few weeks he's has been chewing it. I have got some hibiscrub and cream from the vet and been keeping it clean. I have also been putting a tiny sock like bandage on it but he's now realised he can chew this off and start chewing his tail again. Today he has chewed it so bad I just don't know what to do anymore. Everytime it starts to heal he chews it and were back to square one. He has plenty to do and is out several hours each night. The last 3 days he'd not touched it but then today he's made a right mess of it again



Any advice would be greatly appreciated because I'm all out of ideas.



Thanks