Babychi,
Unfortunately, some chinchillas, particularly males, will do what you are describing. This is, of course, a mating behavior, but also a dominance behavior. I have not yet heard anyone describe an effective technique for changing this behavior. Getting him a cage mate MAY lessen it, or it may not. However, I would not recommend getting him a female mate unless you are prepared to breed chins. Remember, these are rodents, and breeding is what rodents do best
There are a lot of things to think about when talking about breeding chinchillas. It is a lot of fun, but it can also be VERY expensive and heartbreaking. A lot of things can go wrong with a chin pregnancy and you have to be prepared to handle them financially, emotionally, and time-wise. Do you have a minimum of $500 to spend on a veterinary emergency? Are you prepared to hand feed kits every two hours round the clock for weeks at a time? Can you deal with a still-born kit? All of these things are possibilities in breeding, and if you are not prepared for them you shouldn't do it.
I am not trying to discourage you, if you feel like breeding is something you could be passionate about and enjoy. But it is crucial that new breeders go into things with their eyes wide open and fully aware of the possible negative aspects of breeding. Even if everything goes perfectly, as it most often does, there is still the responsibility of ensuring good homes for the kits. If you can't find suitable homes for them are you prepared to keep them and care for them for as long as it takes to find them a home?
If you can honestly answer yes to all of the questions I have posed, then you may be emotionally ready for breeding and I would encourage you to start doing some serious research about chinchilla husbandry and genetics. There is a lot to learn about breeding quality chinchillas. I am sure any of the breeders on this site would be happy to answer any questions you have about the breeding experience and what you need to know before you begin breeding.