A doubt niggled at her.

一丝疑惑困扰着她。

It niggled him that she had not phoned back.

她没给他回电话，这使他有些不安。

The puzzle niggled away in Arnold's mind.

这个谜团在阿诺德脑海里挥之不去。

Part of its purpose will be to iron out the kind of differences that have niggled over the past few months.

委员会的部分意图将解决过去几个月一直找岔子的分歧原因。