1. (长时间地)使不安，使烦恼
If something niggles you, it causes you to worry slightly over a long period of time.

2. 对…吹毛求疵;挑剔
If someone niggles you, they annoy you by continually criticizing you for what you think are small or unimportant things.

1. argue over petty things

e.g. Let's not quibble over pennies

Synonym: quibblepettifogbickersquabblebrabble

2. worry unnecessarily or excessively

e.g. don't fuss too much over the grandchildren--they are quite big now

Synonym: fussfret