small fry vs child

small fry and child both are nouns.

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

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

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

small fry (noun)	child (noun)
someone who is small and insignificant	a young person of either sex
a young person of either sex	a human offspring (son or daughter) of any age
	an immature childish person
	a member of a clan or tribe