Gacho is a colloquial and somewhat informal word that means "lousy," "bad," or "unpleasant." It's a great example of everyday Spanish slang that adds a lot of flavor to the lyrics.
In the song, Mario Bautista sings, "Estar sin ti se siente gacho" (Being without you feels lousy). It perfectly captures the raw, relatable feeling of missing someone so much that everything feels a bit off and unpleasant without them.
Ever made a call you regretted the next morning? That's exactly where this song starts! In "Perdón," which means "Sorry," Mario Bautista and Leon Leiden sing about calling an ex-girlfriend while drunk. The singer apologizes, explaining he went out with his friends to try and forget her, but it didn't work. Being without her feels awful, or "gacho" as he says in Spanish slang.
He tries to act strong and pretend he's okay, but he admits he can't last another night without seeing her. He confesses that missing her—her touch, her kisses, her hugs—has become a "necesidad," or a necessity. He even had a bad dream that someone else was kissing her! The song is a heartfelt, and slightly messy, confession of regret and a desperate plea for her to come back.