Definition:
The verb "niggle" means to worry or complain about small, unimportant things. It can also refer to arguing about minor details, often in a way that seems unnecessary or excessive.
In more advanced contexts, "niggle" can be used to describe a persistent but minor annoyance or worry. For instance, you might say, "A nagging feeling began to niggle at her conscience."
While "niggle" does not have widely recognized idioms or phrasal verbs associated with it, it is often used in phrases like: - "Don't niggle over the small stuff." (Meaning: Don't worry about minor issues.)
In summary, "niggle" is a word that describes worrying or complaining about things that are not very important.