How can I correct this empty space on my right butt cheek? (Photo)

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 improve your buttocks, 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 :)

There are multiple reasons there is still a dimple post-BBL. It is possible that the fat cells did not take to that area. However, I would recommend speaking to the surgeon who performed your BBL procedure about your concern. He will be able to recommend the best course of action. This issue may be able to be corrected with a revision procedure, but your surgeon would be the best person to make that call.