Pegaditos is the diminutive form of pegado, which means "stuck" or "glued". In songs and everyday speech, it's a very common and affectionate way to describe two people dancing extremely close together, as if they were stuck to each other.
In the song, KHEA uses this word to create an intimate scene, singing, "Te hice una canción para que bailemos pegaditos" (I made a song for you so we can dance very close). It's a fun, flirty word that perfectly captures the feeling of a slow, romantic dance.
Ever check your phone at 3 AM wishing an ex would call, even though you know you two are completely toxic together? That is the exact mess Argentine rapper KHEA and María Becerra are stuck in on "Te Necesito" (I Need You). KHEA kicks things off with his brain spiraling: "Me está matando la ansiedad / Siento la necesidad / Vives dentro de mi cabeza / Pero en mi pieza no estás" (Anxiety is killing me / I feel the need / You live inside my head / But you're not in my room). Notice he says "pieza", which is everyday Argentine slang for bedroom. He admits he drinks with his friends specifically so he won't dial her number ("Que para no llamarte lo necesito"), but his mind immediately jumps back to "ese booty tremendo" (that incredible booty) and the endless arguments they used to have in bed.
María Becerra answers back with brutal honesty. She confesses she can barely stand being away from him, singing "Papi, yo te necesito / Si estoy lejos tuyo no resisto" (Daddy, I need you / If I'm far from you I can't resist). But right after admitting that, she hits the brakes with "¿Pero para qué quiero ir a buscarte? / Si tu love está por matarme" (Why do I want to go find you? / If your love is about to kill me). They both know the spark is dying, yet KHEA still offers to write her a track so they can dance close against the wall ("contra la pared"). It is an honest, push-and-pull conversation between two people who crave each other's physical presence, even while admitting that walking away is the only sane choice.