is there any pain associated with it? run your fingers along the side and top and feel for any bumps or active response from him. does the tail always stay like that? dont try to move the tail though just incase it is broken or something and if there is any swelling at all you'll need a vet to do x-rays
there can be many possible benign causes for a tail to be like that however you wont really know unless you get it checked out. If it doesnt seem to bother him and he does everything else a beardie should do i wouldnt worry too much about it. if it does change or you take him in let us know.