Idiom
be a thorn in someone's side
Theme: ANNOYANCE
to be a constant bother or annoyance to someone.This problem is a thorn in my side. I wish I had a solution to it.John was a thorn in my side for years before I finally got rid of him.
Idiom
be a thorn in someone's sidebe a thorn in (someone's) flesh/side
someone or something that keeps annoying you or causing you trouble.A relentless campaigner, he was a thorn in the government's side for years.