Blinda'o is a common slang contraction of the word blindado, which means "armored" or "bulletproof". It's a cool, modern word you'll frequently hear in urban music genres like reggaeton.
In the song, Rauw sings, "Mami, blinda'o de pies a cabeza" (Mami, armored from head to toe). He's using this powerful metaphor to describe how he's emotionally guarding himself after a heartbreak, creating a vivid image of wearing emotional armor to protect himself from getting hurt again.
Puerto Rican singer Rauw Alejandro hits that agonizing phase of a breakup where your phone is practically glued to your hand. In "LEJOS DEL CIELO", he is calling non-stop, stuck in a weird limbo where time drags: "No corren las manecilla' del reloj" [The clock hands aren't moving]. He admits that she leaves him suspended in mid-air, but totally disconnected from paradise: "Me tienes en el aire volando, pero lejos del cielo" [You have me flying in the air, but far from heaven]. He has written over ten drafts of a letter to explain himself, yet he still wonders if all the money in the world matters when you are falling apart inside: "Solo llorando, pero en un ferro" [Alone crying, but in a Ferrari]. In Puerto Rican street slang, calling an expensive sports car a ferro (short for hierro, meaning iron) adds a sharp, funny contrast between luxury and total misery.
Instead of staying home and moping forever, he heads out to numb the pain. He hits the nightlife with his defenses up: "Mami, blinda'o de pies a cabeza" [Baby, armored from head to toe]. You can picture him trying to look tough while grinding in a dark corner of the club ("guayando spotea'o en una esquina", using the island's classic reggaeton slang guayar for close dancing). Other women want his attention, but his heart is still broken behind that cool exterior. Even though he boldly begs for one last night together, he finally admits that losing her hurts less than staying stuck in this endless waiting game: "Aunque perderte da miedo, en verdad mejor dime que no" [Even though losing you is scary, really, you better just tell me no].