Buccal fat
A cheek fat pad. Removing it is permanent, and that is the point to sit with.
The buccal fat pad is a discrete lump of fat in the lower cheek, between the cheekbone and the jaw, distinct from the fat that sits under the skin. Removing it — buccal fat extraction — narrows the lower face and makes the cheekbone read higher by taking away what was below it. It is a real operation with a real effect, and the effect is permanent: the pad does not grow back, and a face that loses volume with age loses it from a lower starting point. That is why surgeons have grown notably more cautious about performing it on people in their twenties, whose faces have not finished changing. Weight loss changes the cheek too, and reverses. If your question is how wide your lower face measures rather than what to do about it, that is a number, and it is free here.