A fixed phrase meaning 'none of your business' or 'don't meddle' used to tell someone not to interfere; often ironic or sarcastic.
そんなことを言うのは大きなお世話だ。
Telling me that is none of your business.
彼女の失敗についてあれこれ言うのは大きなお世話だよ。
Commenting on her mistakes like that is none of your business.
親切のつもりでも、度が過ぎると大きなお世話になる。
Even if you mean well, if you go too far it's meddling.