Castigo means "punishment." It's a powerful, emotional word that you don't often find in romantic pop songs.
In "Cuando Nadie Ve," Morat describes a secret love affair. The singer calls it "nuestro castigo" (our punishment) to have to "fingir que somos amigos" (pretend that we are friends) in public. This word perfectly captures the bittersweet pain and central conflict of their hidden relationship.
Morat, a fantastic band from Colombia, tells the story of a secret and painful love in this song. The singer fell for someone hard, saying, "Me derretiste con esa mirada" [You melted me with that gaze], but that perfect summer turned into a cold winter when he realized she was with someone else. Now, he's accepted his part in this hidden romance: "Nos queremos cuando nadie ve" [We love each other when nobody sees].
To the outside world, they have to act like they're just friends, which he calls "nuestro castigo" [our punishment]. If anyone asks about her, he's prepared to lie and say it's not true "que duele por dentro que no estés conmigo" [that it hurts inside that you're not with me]. It's only in their secret moments, "cuando no haya testigos" [when there are no witnesses], that he can promise her his whole life.