Problemón is the augmentative form of problema (problem), making it a 'big problem' or 'huge mess'. It's a very colloquial and expressive word that instantly sounds dramatic and engaging.
In the song, Álvaro Díaz and Rauw Alejandro use it to describe a secret, forbidden relationship. The whole affair is a problemón because it has to be kept hidden from everyone, especially the girl's boyfriend, which creates a tense and exciting vibe throughout the lyrics.
"Problemón" literally means "a huge mess" or "a big problem," and that is the whole plot here. Álvaro Díaz and Rauw Alejandro are caught up in a secret fling that could blow up their lives at any second. The rule is strict: don't talk about him around your friends, keep your phone quiet until late at night, and keep everything off social media. As Álvaro puts it, "Si ellos se llegan a enterar va a ser un papelón" ("If they find out, it is going to be an embarrassing scene"). The Puerto Rican slang papelón means making a complete fool of yourself in public, and nobody wants that drama.
The lyrics are packed with funny, relatable pop-culture moments. At one point, Álvaro jokes, "Tú tienes más opciones que 12 Corazones" ("You have more options than 12 Corazones"), shouting out the classic Spanish-language dating game show where contestants pick between twelve potential matches. Later, Rauw paints a hilarious, chaotic scene where "Netflix nos estaba preguntando si todavía seguimos mirando" ("Netflix was asking us if we were still watching") right before the girl's boyfriend starts knocking on the window outside. He even drops a nod to reggaeton legend Don Omar with "ojitos chiquitito' como decía Don" ("tiny little eyes like Don used to say") while setting their secret hangout on the shores of Boquerón beach in southwest Puerto Rico. It is pure, sneaky trouble, but neither of them can seem to quit it.