niggles
/ˈnɪɡ.əl/
动词
（通常指长时间）使烦扰，困扰
One thought kept niggling at her.
有一个想法总让她困扰。
挑剔，对…吹毛求疵
She niggles endlessly over the exact pronunciation.
她对发音是否准确挑剔个没完没了。
/ˈnɪɡ.əl/
名词
疑虑；烦恼
Don't you feel even a slight niggle about the morality of your experiments?
你们难道丝毫不担心你们的实验是否合乎道德吗？
小牢骚，小意见
I do have a few minor niggles about the book, but generally it's very good.
对这本书我确实有几点小意见，但总的说来它是很不错的。