Correcting asymmetrical butt cheeks.

It's not uncommon for people to have different sized muscles in the buttocks. That can either be congenital or it could be due to an injury to the muscle. In this case the asymmetry is quite significant. In this case, I would advise the correction of this with buttock fat injections.

Allow me to answer your question as best i can based upon your photos. However, please keep in mind that an in-person consultation with physical exam is first necessary before any legitimate evaluation or final surgical recommendations can be made.
That being said, your are way too lean for fat transfer and it will be a guarentee failure. The only way to correct this much volume asymmetry is with a buttock implant, custom design if necessary. Buttock implants also provide a permanent result whereas most fat transfer melts away within the first 9-12 months. Finally, do not let any surgeon tell you to gain weight for fat transfer as this always fails as well unless you are willing to stay 20+ pounds overweight post-operatively forever.  Hope this helps. 

Hello dear!
Thanks for the pictures and provided information as well.
Based on your photos, you are a good candidate for fat transfer to fix your problem, and I think you'll get very good results. 
l recommend you to make an in-person consultation with a board certified plastic surgeon for a proper answer and to talk about your goals and anything you need to know.
Good luck :)