Sino translates to "destiny" or "fate". While it can also mean "but" or "except" in other contexts, in this song, it refers to one's predetermined path in life.
Darío Gómez uses sino to emphasize the idea that certain things are meant to be, regardless of when or how they happen. He sings, "Cada persona en el mundo tiene su sino" (Every person in the world has their destiny), highlighting the song's central theme that what is meant for you will ultimately find you.
Darío Gómez's "Lo Que Va A Ser Para Uno" is a beautiful song about destiny and finding your soulmate, even if it takes a while! The singer doesn't blame fate for meeting his love "tan demasiado tarde" [too late]. Instead, he's just happy they found each other at all, saying, "qué importa ya no habernos conocido antes" [what does it matter that we didn't meet before].
He truly believes that "lo que va a ser para uno, se lo tiene que encontrar" [what is meant for you, you have to find], no matter what path you take. It's a comforting thought, isn't it? He even says his heart was unknowingly waiting for this person, "para ti, vidita mía, lo tenía que guardar" [for you, my dear, I had to keep it]. It's a sweet declaration of a love that feels truly meant to be, celebrating the perfect connection he's found.