small fry vs nipper

small fry and nipper both are nouns.

Word	Noun	Adjective	Verb	Adverb
small fry	Yes	No	No	No
nipper	Yes	No	No	No

As nouns, small fry and nipper are synonyms defined as:

Other synonyms of small fry include child, fry, kid, minor, nestling, shaver, tiddler, tike, tyke, youngster.

small fry (noun)	nipper (noun)
someone who is small and insignificant	a grasping structure on the limb of a crustacean or other arthropods
a young person of either sex	a young person of either sex