niggle
verb (used without object)
to criticize, especially constantly or repeatedly, in a peevish or petty way; carp.
Used to express a completed action that took place before another specific past action occurred.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
All throughout my scheming since my second return from 75, the prospect of what to do with all the money had niggled away at the back of my mind.
From A Place so Foreign by Cory Doctorow