thorn in the flesh/one's side, a

thorn in the flesh

A constant or persistent cause of annoyance, frustration, or trouble. My little brother is such a thorn in the flesh—he always wants to do stuff with me, especially when I'm trying to hang out with my friends.
See also: flesh, thorn

*thorn in someone's side

 and *thorn in someone's flesh
Fig. a constant bother or annoyance to someone. (*Typically: be ~; become ~.) This problem is a thorn in my side. I wish I had a solution for it. John was a thorn in my flesh for years before I finally got rid of him.
See also: side, thorn

thorn in the flesh/one's side, a

A source of constant irritation. This expression appears in several books of the Bible; in the Book of Judges (2:3) it refers to enemies who “shall be as thorns in your sides,” and in the New Testament Paul refers to his infirmities as “given to me a thorn in the flesh” (2 Corinthians 12:7). The term remains current.
See also: flesh, thorn