My left side cheek muscle are undeveloped. What can I do for this? (photo)

Thanks for your question. For this type of facial asymmetry two dermal fillers are the best. I wound consider Restylane Lyft and/or Sculptra. You can also consider surgery with fat injections, but I believe you will still need fillers in the future because you will continue to age.Best wishes, Dr. ALDO

 Hi, I have performed many facial shaping procedures using dermal fillers, silastic facial implants (cheek implants, chin implants, lip implants), liposuction and/or facelifts for over 30 years.  From the photos, your cheeks are very flat in the front (the left is more flat than the right) due to lack of bone volume not lack of cheek muscles, the chin is weak as are the mandibular angles.  These combine to create an elongated, oval shaped face.     Following my beauty principles, men look chiseled and handsome with angularity in the cheeks, chin and mandibular angles.  The following procedures would create a more ruggedly handsome face.
Cheek augmentation with silastic cheek implants to add angularity to the cheeks and mid face.  
Chin augmentation, using a chin implant, to add projection to the chin creating harmony and balance to the lower face.  I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.  When the chin is weak, this creates an imbalance making the nose appear larger, the mid face top heavy, the lower face looks short, de-emphasizes the lips and allows early formation of a "double chin".  Proper placement of a silastic chin implant adds forward projection to the chin thereby creating harmony and balance to the lower face.  Using the same incision, liposuction can be performed to reduce the fat and further shape the neck.  Excess skin, from below the chin, can also be removed through the same incision.  I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty (requires extensive tissue dissection, bone cuts and placement of metal screws and plates to secure the cut bone segments).  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  In my opinion, you are a good candidate for chin implant surgery.  
Augmentation of the mandibular angles using a dermal filler (jaw implants have too many unwanted side effects IMHO) to add volume, angularity and flare to the jaw line.
Hope this helps