Oh my next girl
Yeah
My next girl

from The Black Keys – Next Girl Lyrics on Rap Genius

Meaning

He is thinking about what his next girlfriend is going to be like/how different she will be from his previous one.
This is a good summary to the song, as it resembles the theme of the song, as well as summing up the story, and showing that the author has undergone some character growth.
This is shown because he is done pining over the previous girl, and started thinking about the next.

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