piffling vs niggling

piffling and niggling both are adjectives.

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

As adjectives, piffling and niggling are synonyms defined as:

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

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