I have performed many Cheek Augmentations using Cheek Implants for over 20 years and exclusively use silastic implants. You seem to be referring to the area of the zygomatic arch and lower temple however, cheek implants are not typically placed in that region.
There is a major branch of the facial nerve that crosses the zygomatic arch but unless you can feel the edge of your cheek implant close to that region, the nerve is most likely not engaged. Moreover, motor nerves, like the facial nerve don't trigger headaches. There is a branch of the trigeminal nerve called the infraorbital nerve that's just below the eyesocket along an imaginary vertical line drawn through the middle of the pupil. If the cheek Implant is pressing on that sensory nerve may trigger trigeminal neuralgia headaches. You would also experience some numbness of the upper lip. The exact position of the cheek implant could, most likely, be determined during examination of the cheek implants by an experienced plastic and cosmetic surgeon. The implants could be removed at any time which is the beauty of silastic implants, IMO.