There's a similar thread discussing it before : http://bar-barians.forumotion.com/t2946-chest-problem
Depending on your injury, that may have had some impact on your musculature.
Couple of other thoughts, overall you will have a dominant side - this will naturally be slightly bigger unless you do a lot symmetrical training (More-over since you have been injured you might not have used your right side as much, thus causing some wasting...)
A Simple thing to improve size is just normal press-ups/dips etc and focus on making sure your form is correct and not working the left side more...
You can also try focusing on (assisted)one-arm press-ups for right side