niggle vs pettifog

niggle and pettifog both are verbs.

Word	Noun	Adjective	Verb	Adverb
niggle	No	No	Yes	No
pettifog	No	No	Yes	No

As verbs, niggle and pettifog are synonyms defined as:

Other synonyms of niggle include bicker, brabble, quibble, squabble.

niggle (verb)	pettifog (verb)
argue over petty things	argue over petty things
worry unnecessarily or excessively