picayune vs niggling

picayune and niggling both are adjectives.

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

As adjectives, picayune and niggling are synonyms defined as:

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

picayune (adjective)	niggling (adjective)
(informal) small and of little importance	(informal) small and of little importance