grievance vs niggle

grievance

noun
  • A complaint or annoyance. 

  • A formal complaint, especially in the context of a unionized workplace. 

  • Feelings of being wronged; outrage. 

  • A wrong or hardship suffered, which is the grounds of a complaint. 

  • Violation of regulations or objectionable behavior. 

  • Something which causes grief. 

niggle

noun
  • A minor complaint or problem. 

verb
  • To use, spend, or do in a petty or trifling manner. 

  • To dwell too much on minor points or on trifling details. 

  • To fidget, fiddle, be restless. 

How often have the words grievance and niggle occurred in a corpus of books? (source: Google Ngram Viewer )