I can see the picture if I click on it (shows as a broken thumbnail at first for some reason). It looks like the tail tip is damaged, but the tail is also shedding. I'd keep a close eye on it but wait out the shed and see what the tail looks like afterward. If the damage is contained to the tip of the tail, it may not cause any long term problems. If you see an open wound, or if the damage appears to be moving up the tail, then it is a good idea to have a vet take a look in case of infection.