Refers to the bony part of the cheek. Often used in contexts like swelling or injury.
I fell and hit my cheekbone.
He was punched and his cheekbone swelled up.
Compound of 頬 (ほお, 'cheek') and 桁 (げた, 'beam' or 'crosspiece'), likely referring to the prominent horizontal ridge of the cheekbone. The exact historical derivation is uncertain.