This is common for everybody. To make this as simple as possible, unless someone is born with perfect genes (impossible to find), then we all have imbalances. No matter how much you try to train your ‘weak’ side, it will never be exactly or as good as the other one. Some people can use both of their arms with the same skill and effort, but even then they are not equally matched. Same goes for the eyes, shoulders, legs, etc. With proper training you can strengthen your weaker side, but like I said it will never be exactly as the stronger or more dominant one. Genetics play a big role here and there is really not that much you can do about it.