child prodigy vs small fry

child prodigy and small fry both are nouns.

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

As nouns, small fry is a hypernym of child prodigy; that is, small fry is a word with a broader meaning than child prodigy:

Other hypernyms of child prodigy include child, fry, kid, minor, nestling, nipper, shaver, tiddler, tike, tyke, youngster, prodigy.

child prodigy (noun)	small fry (noun)
a prodigy whose talents are recognized at an early age	someone who is small and insignificant
	a young person of either sex