Otokonoko (男の子) means "boy." This word specifically refers to a male child. It's a combination of "otoko" (man/male) and "ko" (child), clearly indicating a young person of the male gender. You would use it when talking about young males. Example: あそこに男の子がいます。(Asoko ni otoko no ko ga imasu.) = There is a boy over there.

子供の男性を指す言葉です。「男」と「子」でできています。例：あそこに男の子がいます。