At least from the photos provided, it would appear that the use of a low viscosity, malleable, cohesive HA filler expertly injected in the depression would create the desirable smooth transition between the two areas of the cheek. When it comes to the use of the various, expensive energy-based gizmos, such as fraxels and RF devices that may be hawked to you, you would be wise to exercise a healthy amount of buyer beware, since the hard science behind these "bells and whistles" lags woefully behind the heavy marketing and social media buzz to promote them. Microneedling, which I have been performing for nearly a quarter of a century is best reserved for very superficial surface textural and/or color Irregularities; it is unlikely to be of much value here. I would also be reluctant to dissolve the filler currently there with hyaluronidase (assuming even that it was a hyaluronic acid-based filler), as this might also affect the normal hyaluronic acid as well and might cause some unwanted sagging and crinkling. You would be wise to consult with an experienced, board certified cosmetic dermatology filler expert. Hope this helps and best of luck.