noun
dimple on one cheek
Refers to a dimple that appears on only one side of the face when smiling.
彼女は笑うと左にだけ片えくぼができる。
When she smiles, a dimple appears only on her left cheek.
えくぼ is a general term for dimples, often implying both cheeks; 片えくぼ specifically means a dimple on only one side.
Compound of 片 (kata, 'one side') and えくぼ (ekubo, 'dimple'). The origin of えくぼ is uncertain, but it is a native Japanese word.