Tapo comes from the verb tapar, meaning "to cover" or "to block out". While the word itself is common, its use here is part of the famous Spanish idiom: "tapar el sol con un dedo" (to cover the sun with a finger).
This phrase describes a futile attempt to hide something obvious and immense. In the song, the singer uses this powerful metaphor to express how he's trying to deny that he misses his ex, an impossible task, much like blocking out the entire sun with just one finger.
Have you ever tried to move on from someone, but got stuck on one tiny detail? That's exactly what Venezuelan artist Lasso is singing about in "Ojos Marrones". He's on a date with someone new, and on paper, she's perfect. She laughs at his jokes, gets along with his friends, and they never argue. It's everything he thought he wanted.
But there's a problem. He keeps trying to convince himself, "Estoy bien" (I'm okay), but he can't shake the memory of his ex. The new relationship feels colorless, like the world has turned to black and white. The breaking point comes when he looks at his new date and realizes the simple, heartbreaking truth: "Pero cuando la miro a los ojos / Veo que no son tus ojos marrones" (But when I look her in the eyes / I see they're not your brown eyes). It turns out that one specific thing makes all the difference, and without it, "Nada es igual" (Nothing is the same).