My Son Met An Accident When He Was 2 Year

My son met an accident when he was 2 year old, He got brain injury on left side. Now he is 8 year old and his right hand looks smaller than left hand almost 3- 4 cm. He will use his right hand when he feell nessasary to use,Otherwise he will use his left hand only. I heard in child hood it is possible to clear such issues.

Kindly give me an answer ??