귀에 못이 박히도록 들어요 · 귀에 못이 박히도록 들었어요
to hear something over and over, to be told a million times
Example
공부하라는 말은 귀에 못이 박히도록 들었어요.
I've been told to study a million times.
Word parts
This 못 is a callus, not a nail: hearing something constantly gives your ears calluses.
Good to know
Almost always used as 귀에 못이 박히도록 (or 박히게) + 듣다/말하다.