post-pubescent
/ˌpəʊs(t)pjʊˈbɛsnt/adjective
Of a young person: having (especially recently) been through puberty. Also: of or characteristic of the period in a person's life immediately following puberty.
noun
A young person who has (recently) been through puberty.
Origin
Early 20th century; earliest use found in American Anthropologist. From post- + pubescent.