"Quítate La Careta" (Take off the mask) is a breakup song with its gloves off. Voz de Mando is singing to an ex who blew up the relationship and is now playing the victim for everyone watching.
The opening line sets the tone: "No te queda que te hagas la inocente ante la gente" (Playing innocent in front of people doesn't suit you). Here no te queda is a handy Mexican Spanish idiom: literally "it doesn't fit you", like clothes, so it means "that act doesn't suit you." He accuses her of posting that she is always the good one, while her photos only show "lo que aparentas" (what you pretend to be).
The chorus is the fun part. "Y ya no cubras lo infeliz con maquillaje" (And stop covering up the unhappiness with makeup), and then the sarcastic jab "Si ganaste el premio Nobel, por chantaje" (If you won the Nobel Prize, it was for blackmail). It's petty, and that's exactly why it works. He tells her to "corre y sigue tu viaje" (run along and keep going on your way), and the last line twists the knife: "que llegó tu suplente" (because your replacement has arrived). Watch for corriente, which here means "tacky" or "common", not "current."