Baldy tail..

Louie has seemed to have gained a bald bit on one side of his tail - on the tip.. It's not spreading, it's not itchy or sore and he isn't chewing it..

I did think it was the constant wagging and banging on doors that had done it but it's only on one side..

I'm not overly worried about it yet, it has been there a week or so.. I thought it could have been where he ripped the fur off on a walk - but when he did it to his leg at the last Dogsey walk - it looks totally different..

Any ideas?