Coqueteo translates to "flirting" or "flirtation". It's a fun and engaging word that captures a specific type of romantic interaction.
In the song, Christian Nodal uses it to describe the playful, yet ultimately non-committal, interactions he had with someone else. He sings, "Puro coqueteo ¿y pues yo que hacía?" (Pure flirting, and what was I to do?), implying that it was just lighthearted teasing and nothing serious, despite what others might have said.
Christian Nodal's "No Te Contaron Mal" is a confession set to a regional Mexican beat. The singer answers, point by point, the questions his partner already has after hearing rumors from a friend: yes, there was a kiss, yes, he was with someone else for one night, but he insists it went no further and that it happened during a rough patch in the relationship.
The hook plays with the double meaning of the title, "they didn't lie to you." Instead of denying the story, he confirms it while minimizing it. He shifts blame to the breakup itself and to having been drunk, landing on the line "una no es ninguna" -- one time doesn't count.
It's a song about a man justifying himself more than apologizing, wrapped in the bravado typical of the genre.