I had that problem with my budgie and took him to the vet to see if there was some cut, bruise, etc. that might be caused by the band and causing him to chew at it. There was nothing. She and I talked about removing the band altogether, as it should ONLY be done by an avian veterinarian. She advised against it, primarily because he's a budgie and his leg is so small there's always the risk of breaking his leg during removal of the leg band. He would also have to be anesthetized to ensure absolute stillness while removing the band...all of which brings a risk.
In short, our vet advised against it unless there's a serious problem with the band, as the risks of injury during removal are pretty high. I believe Bob is a cockatiel, so there may be less risk, but as a smaller bird there is likely some risk still. I'd talk to an avian vet about it and see what they recommend. It really is something that only they should do. All the literature I've read says bird owners should NEVER try to remove a bird's band themselves.
I will say, that Keats has since started leaving his band alone. He's molting now, and in puberty, so his toys are much more interesting to him.