Ofrezco comes from the verb ofrecer, meaning "to offer". In this context, it's used in the first person singular, "I offer myself", which is a very direct and bold statement.
In the song, the singer is trying to convince someone to leave their current partner. He sings, "Si tú quieres yo me ofrezco" (If you want, I offer myself), implying he's ready and willing to step in and fulfill all the emotional and physical needs that her current partner isn't meeting. It's a key word that drives the song's central theme of seduction and proposition.
Have you ever been in a relationship where you felt unappreciated? In "Si Te Falta Alguien," Christian Nodal sings from the perspective of a man who sees a woman being neglected by her partner. He tells her to stop pretending she's happy, pointing out that her boyfriend doesn't even know how to love her properly.
Instead of just feeling sorry for her, he makes a bold offer. He tells her to use him as a "pretexto" (an excuse) to finally leave her bad relationship. He volunteers to be the person who gives her the affection and passion she's missing, promising, "Conmigo no te va a faltar amor" (With me, you won't lack for love). It's a direct and confident plea for her to take a chance on him and find the happiness she deserves.