What can I treat for this depress scar after scar removal surgery?

Sorry this has happened to you, but frankly not particularly surprised. I have been cautioning my regular followers for years that scar revision surgeries, particularly in areas subject to a great deal of static or dynamic tension (such as the cheeks) runs the risk for the development of stretch scars and even tram track stitch marks.
That being said, for the depressed portion of the scar, subcision, which I have been performing for all kinds of indented scars from acne, chickenpox, trauma and surgery (as in this case), can be used to elevate and smooth the scar. Following this, professionally performed manual miicroneedling (no need for the added expense and risks of RF microneedling) can be peformed to help blend better any residual surface, superficial texture and color irregularities with the surrounding normal skin. You would be wise to consult with a board certified cosmetic dermatologist and best of luck.