on case

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on (one's) case

Constantly or frequently nagging, harassing, or annoying someone. My boss has been on my case all week to get that report done. I'm sorry for getting on your case about it, but I need an answer soon.
See also: case, on

*on someone's case

 and *on someone's back
Inf. harassing someone about a personal problem; annoying someone. (*Typically: be ~; get ~; keep ~.) I'll get on Tom's case about being late so much. I'm sorry, I won't get on your case anymore.
See also: case, on

on (someone's) case

Persistently nagging or urging someone to do something.
See also: case, on