fiddling vs petty

fiddling is not a noun while petty is a noun.

Word	Noun	Adjective	Verb	Adverb
fiddling	No	Yes	No	No
petty	Yes	Yes	No	No

As adjectives, fiddling and petty are synonyms defined as:

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

fiddling (noun)	petty (noun)
	larceny of property having a value less than some amount (the amount varies by locale)

fiddling (adjective)	petty (adjective)
(informal) small and of little importance	inferior in rank or status
	contemptibly narrow in outlook
	(informal) small and of little importance