be a thorn in (someone's) side

To be a constant or persistent cause of annoyance, frustration, or trouble. My professor was an environmental activist when he was younger, and, apparently, he was quite a thorn in the oil companies' sides at the time.

Common Names:

Name	Pronounced	Usage
Ashleigh	ASH-lee	English (Modern)
Dan (2)	DAN (English), DAHN (Romanian, Czech, Swedish)	English, Spanish, French, Portuguese, Romanian, Czech, German, Polish, Swedish, Danish, Norwegian
Ji-U	jee-oo	Korean
Beyza	-	Turkish
Shanae	shə-NAY	English (Modern)
Euphemios	-	Ancient Greek