Ombligo literally translates to "belly button" or "navel". It's an interesting and somewhat unexpected word to find in a song, especially in a context describing emotional pain.
In the lyrics, Cami sings, "Me duele hasta el ombligo si escucho tu voz" (It hurts me even to my belly button if I hear your voice). This vivid and somewhat unusual expression emphasizes the depth and intensity of her emotional pain, suggesting it's a visceral, all-encompassing ache that reaches even the most central part of her body. It's a memorable way to convey profound heartbreak.
Cami opens mid-breakup, standing in the street where she was just left: "Me dejaste sola" ("You left me alone"), watching "tu sombra" ("your shadow") run off looking for a way out. The chorus turns the heartbreak into weather — "Esta noche hace un poco más de frío" ("Tonight it's a little colder") — and the cold reaches all the way down, "hasta el ombligo" ("down to my belly button"), every time his voice comes back to her. She curses him for hours in one line and promises he'll love her forever in the next, then the whole song narrows to a single repeated word: "Hoy" ("Today").