A thorn in somebody’s flesh/side
Definition 1 of 1
Pro Tip 1/3Consistent Irritant
Refers to ongoing issues, not a one-time problem. 
Trying to get a visa has been a thorn in my side for months.
Pro Tip 2/3Negative Emotion
Conveys a sense of frustration or irritation with a person or issue. 
My computer crashes daily, becoming a thorn in my flesh.
Pro Tip 3/3Metaphorical Use
Not a physical thorn, but symbolizes something bothersome. 
His constant jokes about my job have turned him into a thorn in my side.