niggles
nig-gles
verb
To cause slight, persistent worry or annoyance to someone.
"The thought continued to niggle at him."
noun
Small, minor complaints or worries, often insignificant but persistently annoying.
"Just a few minor niggles with the new car."
Thesaurus
Synonyms: pettifog, bicker, niggle, quibble, brabble, squabble, fret, fuss