niggling vs trivial

niggling and trivial both are adjectives.

Word	Noun	Adjective	Verb	Adverb
niggling	No	Yes	No	No
trivial	No	Yes	No	No

As adjectives, niggling and trivial are synonyms defined as:

Other synonyms of niggling include fiddling, footling, lilliputian, little, petty, picayune, piddling, piffling.

niggling (adjective)	trivial (adjective)
(informal) small and of little importance	concerned with trivialities
	of little substance or significance
	(informal) small and of little importance