to worry someone slightly, usually for a long time

I just can't remember his name - it's been niggling me for a couple of weeks. 我就是记不起他的名字——我已经为这个伤脑筋好几个星期了。

One thought kept niggling at her. 有一个想法总让她困扰。

to criticize someone about small details or give too much attention to details

She niggles endlessly over the exact pronunciation. 她对发音是否准确挑剔个没完没了。

The accounts department is niggling me for ten pence they say I owe them. 财务部一直纠缠不休，说我欠他们10便士。

a small doubt or worry

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？

a small criticism

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。