Help

If i understood youre question correctly, then its only because your hampster is growing up, this is a normal thing for hampsters that are changing from a baby, to an adult. If it is already an adult when it started to do this, then he is bored and you should give him something to do, like tunnels, wheels and things to bite on. For example you can get theese big chew bar things which you poke into the side of the cage for the hampster to bite onto. If the hampster has some of theese, or all of theese, then try cleaning out the cage, that could also be a problem, or another thing to try would be to let him out of the cage for a bit, and if this still doesnt help then try to move the cage to another location, because hampsters can be quite territorial, and when they have been in one location for so long, they will start to think that they own that location, and think they are the boss of everything that goes on in that location, so he will bite the bars to show that he is big and hard. And if after moving the cage, he is still biting the bars (which he shouldnt be) then you should really go take him to a vets, and tell the vet you have done everything which i have just told you to do but the behaviour of your hampster still hasnt changed. So dont worry about it, and just follow my simple steps and youre problems should be sorted! I hope i helped