Huellas literally means "prints" or "traces," like footprints or fingerprints. It's a beautifully evocative word with a lot of depth.
In this song, KAROL G uses it metaphorically to deliver a powerful message to her ex's new lover. She sings "Cada que te acaricie, tu piel ya tendrá mis huellas" (Every time she caresses you, your skin will already have my marks), meaning her impact on him is permanent and she can never be truly erased or forgotten.
This is not your typical sad breakup song. Colombian superstar KAROL G is holding nothing back in this fiery message to the woman her ex cheated on her with. She's not crying over him; she's calling her out directly. KAROL G contrasts what she offered in the relationship with what this new woman represents. She sings, "Yo te lo di todo, tú no quisiste nada" (I gave you everything, you wanted nothing), pointing out that he threw away a real commitment for something temporary. The difference is clear: "Ella es un segundo y yo era para siempre" (She is a second and I was forever).
This whole song is a warning shot. KAROL G dedicates it to the new girlfriend, singing "Esta se la hice a ella, ella / Que se cree que por bella, ella / Puede robarme todo lo que nunca tuvo ella" (I made this one for her, her / Who thinks that because she's beautiful, she / Can steal everything from me that she never had). She even warns that her memory will linger, promising that "Cada que te acaricie, tu piel ya tendrá mis huellas" (Every time he caresses you, your skin will already have my marks). The final mic drop is the classic warning: if he cheated with you, he'll cheat on you. She tells her rival directly, "si fue así conmigo / También lo será con ella" (if he was like that with me / He will also be like that with her).