How is the best way to fix this problem of having short infragluteal on the left side and longer on the right side?

Dear Jmnkh86,
it is hard to tell for sure without an examination. In a lot of cases, fat transfer provides good improvement in symmetry. If you are considering a surgery, I would suggest you to consult a board-certified plastic surgeon. Only after a thorough examination you will get more information and recommendations.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Treatment for unevenness of the infragluteal crease much depends upon the reason for the asymmetry, whether it be from a genetic, traumatic, or aging process. If the one buttock cheek is more constricted and thus smaller than the other side then expansion of that side with an implant or series of implants would likely be the best option. If the buttock cheeks are otherwise about the same size then some form of a lower buttock tuck (aka banana-roll plasty) +/- buttock lift may be the best option. One thing that usually should be avoided is trying to utilize liposuction for this particular problem as it usually makes things worse and gives you multiple infragluteal creases. Glad to be of help.

Hello Jmnkh86,
Your answer could be buttlift, Fat transfer, or combination of the two. Its really hard to tell without good photos. I would be happy to evaluate you if you submit good photos. SincerelyDr.G