Can fat transfer to this area fix asymmetrical pecs? (Photo)

Yes you can. Fat will help a lot actually, but keep this in mind: you are very lean and there is not a lot of fat in the areas you highlight so it would likely take two or three rounds of fat grafting to be able to get enough fat to take to fully correct the chest asymmetry.

It's because you cannot just put a big blob of fat and have that work because the fat has to go inside of other fat in order to develop a blood supply and work. In thin beds of fat only small amounts of fat can be added but as the newly grafted fat takes and survives you can add more and more fat on each subsequent grafting to build up the tissue.

Yes, you should get good results with a fat transfer. You may need one or two procedures for best results.