bone to pick, have a - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
An unpleasant issue or grievance that needs discussion. For example, Concerning the room assignments, I have a bone to pick with you. This metaphoric term alludes to a dog worrying a bone. [Early 1500s]