expression, ichidan verb
find fault with trivial things; get angry over trifles; raise one's eyebrows
Idiomatic expression used when someone overreacts to a minor issue, often with a critical or angry expression. The literal image is of raising the outer corner of the eye (目くじら) in displeasure.
彼は小さなミスにいちいち目くじらを立てる。
He finds fault with every little mistake.
そんなことで目くじらを立てるなよ。
Don't get so worked up over such a small thing.