Celda literally translates to "cell," but in the context of this song, it specifically refers to a "prison cell." It's a poignant word that immediately hints at the struggles and hardships the artist faced.
Anuel AA uses this word to reflect on his past, singing, "Para abrazarte como no pude hacerlo cuando estaba en la celda" (To hug you like I couldn't when I was in the cell). This word is central to understanding the song's themes of regret, loss, and the impact of his incarceration on his relationship with his mother.
Anuel AA's "Mi Vieja" is a really personal and emotional song where he's talking directly to his late mother. He wishes he could have her back, especially to give her a hug he couldn't when he was in jail. He sings, "Quisiera tenerte de vuelta / Para abrazarte como no pude hacerlo cuando estaba en la celda" [I wish I had you back / To hug you like I couldn't when I was in the cell].
He feels a lot of regret and pain, acknowledging that his actions caused his mother a lot of suffering. He says, "Porque sé que yo fui parte de tu sufrimiento / Y no me dio tiempo pa' decir lo siento" [Because I know I was part of your suffering / And I didn't have time to say I'm sorry]. He thanks her for always being there for him, even when he was making bad choices, and how lost he feels without her now. It's a really raw look at grief and guilt, and a powerful tribute to his mom.