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.
This song is all about that awful feeling of being in limbo after a relationship goes wrong. Rauw Alejandro is desperately trying to get in touch with someone who isn't answering. He sings, "¿Dónde? ¿Dónde estás? / Llevo rato llamando, contesta" (Where? Where are you? / I've been calling for a while, answer). Time feels like it's stopped for him, and he uses this amazing line to describe the feeling: "Me tienes en el aire volando, pero lejos del cielo" (You have me flying in the air, but far from heaven). He's stuck, and even though he's scared to lose her, he'd rather just get a clear 'no' than be left hanging.
He knows there's been some serious damage done, asking, "Uno perdona, ¿pero quién borra las cicatrice'?" (One forgives, but who erases the scars?). He tries to write a letter to explain himself but keeps deleting it. He even throws in a classic flex, admitting he's crying but "en un ferro" (in a Ferrari). He tries to act tough and says he's bulletproof ("blinda'o de pies a cabeza"), but it's clear he's heartbroken and can't sleep. He's out on the street trying to cool down what feels like an "infierno" (hell) inside him.