Unfortunately, there is nothing you can do for this. The pectoralis muscle attaches to the breast bone on either side. The gap is an anatomical landmark that can not be changed. The bigger and more defined the muscles are the more you will notice it.
The only treatment option for right medial pectoralis muscle margin is fat injections. You can not implant muscle fibers but you can fat which will initially fill it out. Whether the fat will stay in a lean body like yours can not be predicted.
What you exhibit is a normal aberration of the perctoralis major muscle. This is not an uncommon finding however in you because of the propensity of the muscles to be pronounced, this is prominent. I would not recommend surgical alteration of the muscle fibers, however you may benefit from injections of fillers In the area for camouflage or possibly even fat injections.
With very little body fat these bulges and depressions become more obvious. There is no procedure that can correct this problem.
Consult with a board certified plastic surgeon to see if you are a candidate for fat grafting to help camouflage your area of concern.
Thanks for your photos and question. You are obviously quite fit and cut, able to show every nuance of muscle fiber detail quite well. I see what bothers you, but would strive to explain that symmetry is an elusive and uncommon reality.
Just like the veins on the backs of everyone's hands, no two hands (even on the same individual) are exactly symmetrical. The same goes for eyes, hands, etc. Even our faces (as clearly shown by half-mirror photos) have asymmetry that is absolutely normal. I have been measuring breasts for nearly 3 decades, and have found only one or two women whose measurements are the same (and they don't look the same!)
What this all means is that your asymmetry is normal, and is not a sign of maldevelopment, just normal variation. Further, any surgical attempt to reposition or transplant muscle fibers would result in dead or scarred tissue that is not enervated and therefore unable to be "exercised" and bulked-up. Plus, you would have disfiguring scars.
Fat grafting could provide some minimal improvements, but I would think that is a long run for a very short slide, if you'll forgive a baseball analogy!
Your questions is not at all inappropriate, but I hope you understand that this should be abandoned before you do some harm to your fabulous physique that you would regret later! Best wishes! Dr. Tholen
Well you are right in that it is definitely an odd request! You may have developed some atrophy of the muscle fibers from over use or perhaps that is naturally the shape of your muscles that has just become more prominent with years of muscle development from your weight lifting. I don't think any muscle re-positioning procedures will really help you plus you would have to go through a period of muscle rest where no lifting is done, which I am certain you would not want. Additionally, even with a rest period you would risk tearing the repair once heavy lifting resumes. I would suggest consideration of small amounts of fat grafting to fill in the areas where the muscle is deficient to camouflage the area that you dislike. A reasonable and safe alternative that is less invasive and shorter down time. Make sure you consult with a board certified/eligible plastic surgeon with experience in fat grafting procedures to see if you are a good candidate! Good luck!