Everyone has muscular imbalances it is totally normal. If you want to decrease the imbalance the best way is weight training with a really good personal trainer but it is not necessary. Unless you have problems with your neck or something you can easily ignore it.
My therapist told me awhile back that my right shoulders are a bit bigger than my left because I am right handed like you. So it is normal to be imbalance because right handed people who do sports tend to work their right side more. He told me not much can be done, just stretch before hand and properly.