thorn in one's side

a thorn in one's flesh
a thorn in one's side

(a person or thing that repeatedly annoys you or causes you pain; one who thwarts you, one who irritates you, a bug)
— источник постоянного раздражения;
~ кость в горле; ~ бельмо на глазу (источник неприятностей, раздражения); ~ бич; ~ сущее наказание

He's always been a thorn in my side — always critical of me. (IdiomHome) — Он невыносим — достал уже своей критикой.
A relentless campaigner, he was a thorn in the government's side for a number of years.

Related vocabulary:
[cross to bear]
[pain in the neck]
[bane of one's life]
[millstone round one's neck]
[ярмо на шее]
[holy terror]
[сущее наказание]