Sorry to hear that your little ham is having some tail troubles. And dont be sorry for not posting for some time, we all understand we have other lives besides HC (although some people really spend lots of time here heh
) all the same we are glad to be here for anyone that needs help or advice despite how often they post.
I would assume that is has to do with some kind of skin irritation, I know hamsters arent dogs, but as an example dogs can have skin irritations that you cant easily see, especially if its a kind of fungi, (from what I gather) So there may be something you cant visibly see.
The only other things I have heard of for reason why animals chew their tails is because of boredom (although I dont know how accurate that is) or because of some sort of nutrition deficiency in their diet. But Im sure your hamsters diet is fine. I guess your best bet would be a trip to the vets for this one.