Luna Ki is from Spain, and "Putón" is her being as bratty and shameless as she can, half in Spanish, half in English. It opens with a kiss-off: "Tú me hiciste llorar, tú lloraste igual" (You made me cry, you cried too), "pero te da igual porque todo da igual" (but you don't care because nothing matters). Dar igual is one of the most useful phrases in Spanish: me da igual means "I don't care" or "it's all the same to me".
Then it gets silly and cheeky. "Dije 'Fuck Universal', firmé con Universal" (I said 'Fck Universal', I signed with Universal) is a joke about the record label, and "Hello Kitty, bye, ya no estoy" (Hello Kitty, bye, I'm gone) plays with her nickname. The title word putón is a crude Spanish insult for a woman who sleeps around, and she takes it on herself on purpose: "Me siento un putón" (I feel like a total slt). Some lines are very explicit, so this one is for adult listeners. Look out for Spain slang too: "te quiero pila" (I love you loads), where pila means "a lot", and "Cari", short for cariño (darling). "Estoy en Plutón" (I'm on Pluto) is her way of saying she's completely spaced out.