bone to pick
A usually legitimate grievance against a particular person. The offending person either is unaware of the grievance or has been studiously avoiding acknowledging it - usually the latter - and will probably never acknowledge that this is a real, legitimate complaint.
Example:
I've got a bone to pick with you. You really violated my personal boundaries yesterday, and that wasn't cool.
I've got a bone to pick with you. You really violated my personal boundaries yesterday, and that wasn't cool.