to make unnecessary complaints about small matters

nag

to give a judgment of the quality of (something)

disapprove, judge as bad

to look at (a person, thing) carefully in order to learn something; to put questions to (a person) in order to test knowledge or get information

analyse, test

an old horse; to find fault with a person often

harass, bother

to annoy or trouble (a person)

bother, harass

to make a protest; argue in protest

argue against