Uneven sides after gyno surgery. The other side seem to be healing just fine, should I be concerned? (photo)

Hi and welcome to our forum!
The gynecomastia correction involves dissection of the breast tissue from surrounding tissues with the removal of breast tissue. This surgical "insult" results in the inflammation of early healing which is associated with tissue swelling. It will initially obscure the entire result. 60-80% of the swelling will subside by the 6th week, with the remainder slowly dissipating over 6 - 12 months. The swelling will most likely be asymmetric, with one side more involved than the other. Inflamed tissues will be firm....just like residual breast tissue...Initially, you can't tell them apart. As the swelling subsides, any differences due to residual breast tissue will persist while swelling will abate. 
Even if "sure" that there is residual breast tissue, reoperation in an inflamed healing area carries a significant risk of bleeding.
Continue followup with your plastic surgeon. It is too early to tell. 15% of cosmetic surgeries may require a secondary touch up.
Best wishes...