Your picture suggests that you are into Boxing or Martial arts ?If so you might have a zygomatic arch fracture (the bone which spans across the cheek from the lower lid to the ear is pushed "inwards"). If the bone is broken ("pushed in") it needs to be reduced to its original shape and position. THis would require some surgery. Should this be a "soft tissue" problem and not a bone fracture various procedures with "fillers" can be attempted. First though I would have the area checked for a fracture which can be easily done by examination and/or an x ray. Good luck!
What caused this? Did you have trauma in the area? While unlikely, I would ensure there isn't a fracture of the zygomatic arch. More likely is some localized soft tissue necrosis from trauma. In that case, can fill the dent in with something. Ideally you will use your body's own tissue rather than an artificial material. Will also need to separate overlying skin from the deep tissue (subscision as mentioned above is one method) to allow the filler to be placed.One option is to harvest temporoparietal fascia and some temporalis fascia from the just in front of the ear, and through the same incision lift the skin off the deeper tissue and place the grafts.