How can I even out my chest? One side will not grow as fast.?

After high school I started to weight train 4-5 times weekly. As my chest started to grow I noticed the upper part of my right pec will not develop. I have been told use dumb bells to even out, but I was told by the doctor that will not work. My chiropractor said that when I played baseball I partially told a muscle from throwing. It was so minor that I never noticed or experienced pain, but when it grew back it grew back tight. That is why the upper part does not look as full as the other side. I was instructed to massage it in certain parts. I have not done it as consistently as I should. I pretty much only do it when it frustrates me so much from looking at it. Most people don't notice it, but I do and it bothers me. Has anyone else ever experienced this, and what did you do?