I had a cat that the same thing happen, her name was sheba. we treated the cats tail for over a year, nothing helped, finallly the tail had to be amputated, so she then had about 2 inches of tail, everyone ask if she was a bob tail, but the two inches still gave her ballance, which cats need. it was about $400 total for that darn thing, but she lived another 10 years after that, so take yours to the vet and get it checked.
CAT
I'd get him to a vet ASAP. We had a cat who was attacked by something and her tail was pretty mangled. She disappeared for a few days and her tail became quite infected and ultimately had to be amputate. I highly recommend get it checked out ASAP.
Jim