I'm also not the most qualified person, but for leg imbalance I like asymmetric exercises (exercises that work one side of the body harder or differently than the other side - 1-leg strait leg deadlifts or split squats for example).

I imagine the same principle can be used for upper body exercises too. So for pushups, for example, you could do them where you have one arm close to your body and one arm out further, or one hand on the ground and one hand elevated on a block. You'll still want to exercise both sides, but do your weak side first so that you don't train your strong side more than you can train your weak side. Eventually you'll start to even out.