PLEASE ANSWER WHY DO BUDGIES BITE THE SIDE OF THE CAGE I'M WORRIED PLEASE ANSWER

I have a Cockatiel, he does exactly the same thing. Birds bite anything and everything, they use their beaks to feel,plus he might just be cleaning his beak, my Cockatiel does that alot. There is nothing wrong with your budgie, so don't worry.
You can help him buy putting wooden toys in the cage, he can then chew those. They love to chew, it's a natural thing.
Hope that helps?
Mel x

i think it sharpens thier beaks

It keeps the beak from overgrowing and causing serious problems. They also get bored so they bite the cage, or whatever they can. Get some toys in there and a calcium stick that you attach to the side of the cage. Play with it often and it won't hurt itself next. But it is a natural thing for them to bite so don't worry. He isn't in any danger. :)

Your budgie may just be bored but it's beak is probably growing. The best thing for it at this stage is actually Cuttlefish which you can get at all good pet stores.