Please help me. I have an uneven chest.

Many people develop an imbalance as a natural result of having a preferred "writing side". Having an injury can further accentuate this lack of symmetry. It may pay to go and see a physio to check it out as it could also possibly be a rotator cuff impingement.

If it is not the result of an injury then the best way to fix imbalances IMO is to drop back on the weight a little so that you are playing to the strength of your weaker side. Watch your form really closely - this is critical. You should notice the imbalance start to slowly disappear. If you try to lift too heavy, the problem can get worse as your stronger side will take up even more of the work and build at the cost of your weaker side. So perfect your form and moderate your weight.

 

Once you have your balance back, start working harder, but once again watch your form. 

 

You can also explore some therapeutic body balancing modalities which can be very helpful. These include Structural Integration, Feldenkrais, Ideokinesis, Yoga Therapy and Pilates.