Doma comes from the verb domar, meaning 'to tame,' like an animal. In this song, the reflexive form se doma means 'he is tamed' or 'he gets tamed'.
Junior H uses this powerful image in the line, "Si un perro se enamora, ves qué fácil él se doma" (If a dog falls in love, you see how easily he is tamed). It's an unforgettable metaphor for complete vulnerability, expressing how love can make someone surrender their pride and wildness completely.
This song is all about a situationship gone wrong... or right, depending on how you look at it! Junior H kicks things off with the very blunt question, "¿Quién me mata esta bellaquera?" [Who can kill this horniness for me?]. He's hooked on someone who he was only supposed to have a casual thing with. He admits, "Dices que no es de contrato / Que fue sólo pa' un rato" [You say it's not a contract / That it was just for a little while], but he can't stick to the plan. He's caught feelings, big time.
The whole track is him wrestling with this. He's asking himself, "¿Cómo decir que te extraño / Sin decir que te extraño?" [How do I say I miss you / Without saying I miss you?]. He's obsessed with the specific things about her, from her unique tattoo to the way they are together. He even compares himself to a lovestruck puppy, saying "Si un perro se enamora, ves qué fácil él se doma" [If a dog falls in love, you see how easily he's tamed]. It's a funny and honest way to say he's completely wrapped around her finger, and all he wants to know is if she feels the same way.