Candela literally means "candle flame". However, in many Latin American countries, it's popular slang for intense "fire" or "heat", and by extension, a difficult or fiery situation.
In the song's hook, Becky G taunts her ex by singing, "Ahora aguanta candela", which is a powerful way of saying "Now you can take the heat" or "Now deal with the consequences". It's a fiery, memorable word that captures the song's theme of empowerment and taking back control.
Picture this: it is six in the morning, and you are staring at your ceiling because someone did not bother to pick up the phone. In Sola, Mexican-American singer Becky G hits the absolute limit of her patience with the opener, "Otra noche sola en mi cama / Las seis de la mañana y / Tú ni siquiera me llamas" [Another night alone in my bed / Six in the morning and / You don't even call me]. Instead of moping around, she cuts him off completely and decides an empty bedroom is way better than a negligent partner. She tells him to go stay with his friends and let other women watch his house, declaring, "Mejor me quedo sola / Y me voy para la calle" [I'd rather stay single / And hit the streets].
What makes the track stick is how blunt she gets when reclaiming her independence. She hits him with "Te quite la licencia ya no manejas mi destino" [I took away your driver's license, you don't steer my destiny anymore], which turns a breakup into a car repo. Then she drops a great pop-culture reference: "De tu juego me retiro como Kobe" [I'm retiring from your game like Kobe], walking away from his drama just like basketball legend Kobe Bryant walked off the court. She admits she still loves him, but drops the classic reality check, "el amor no quita conocimiento" [love doesn't take away common sense]. She is trading his excuses for a night out with zero regrets.