Pivete is a Brazilian Portuguese slang term that refers to a young kid, often with a slightly mischievous or informal connotation, similar to 'brat' or 'urchin'. It's not a formal word for child, making it more interesting and specific to certain contexts.
In this song, the lyric "arruma um pivete pra chamar de amor" (find a kid to call love) is used provocatively. The singer is telling the ex-partner, who is acting immaturely, to go find someone equally immature to be with, highlighting the contrast between a 'menina' (girl) and a 'mulher' (woman).
This is a song about moving on, and about the moment the person who let you go finally notices you are gone.
The singer opens by saying he has already learned to forget her. Only now, after the fact, does she realise he is missed. Everything he once did for her counted for nothing, so from here on he plans to give that effort to someone who actually cares. The door she shut is the same door the new woman walked straight through.
The chorus draws the comparison the title promises. "You're there, she's here." One of them knocked him down, the other looked after him. That gap, the singer says, is the difference from a girl to a woman: not age, but how a person treats someone who loves them.
The last jab is the sharpest. Until you grow up, he tells her, go find some kid to call your love. He is not asking her to come back. He is telling her he has stopped waiting.
The song is Brazilian sertanejo, and the lyrics use very spoken Portuguese: "'to" for "estou", "'ta" for "esta", "'ce" for "voce", and "pra" for "para". Learning to hear those shortened forms is most of what makes fast Brazilian speech click.