Menuda literally means "loose change" or "small coins". It's a fantastic example of a common word used in a clever and memorable metaphor.
In the song, Blessd sings "Cambiaste un cheque por la menuda" ("You traded a check for loose change"). He's using this phrase to say his ex left him, someone of high value (a check), for someone new who is worth much less (loose change). It's a powerful and slangy way to talk about a breakup.
Colombian artist Blessd gives us a classic reggaeton breakup song with "Mírame". He's talking directly to his ex, and he's not holding back. The story starts with him accepting the end, telling her, "Mírame fijo a la cara si no sientes lo mismo / Que yo entenderé" (Look me straight in the face if you don't feel the same / I'll understand). He even seems to know why she left, admitting, "No cualquiera puede aguantar mi ritmo" (Not everyone can handle my rhythm). It's a mix of sadness and pride. He's hurt, for sure—he says it plainly: "Su adiós duele" (Her goodbye hurts).
But this isn't a simple sad song. Blessd immediately follows up his pain by saying he'll be with other people—"mientras yo me enredo en otras pieles" (while I get tangled in other skins)—and hopes someone else comforts her. He recalls the breakup call where she accused him of cheating over girls he claims he doesn't even follow. He thinks she made a huge mistake, telling her she "Cambiaste un cheque por la menuda" (You traded a check for small change). Despite all the tough talk and pretending he's fine, the song has a moment of total honesty. When he asks himself if the breakup hurt, his answer is simple and direct: "Mi amor, ¿pa' qué le digo que no?" (My love, why would I tell you no?).