N'Zonzi played 90 minutes in Saturday's match as Barca ran out comfortable winners in a crushing victory.
Coach Vincenzo Montella has received significant criticism for the team's listless display, but N'Zonzi perhaps took some of the attention off him when he was photographed in a Madrid nightclub in the early hours of the morning.
N'Zonzi also headed straight down the tunnel at full-time instead of joining captain Sergio Escudero and team-mates in heading over to the Sevilla fans to apologise for the performance.
But the Frenchman issued a hasty apology on Sunday.
"I want to apologise to the Sevilla fans," N'Zonzi said in a video posted to the club's official Twitter account.
"I made a mistake because I left after the game. It's difficult for everyone, for us too.
"What happened is also difficult for the players. We play every three days, I live alone, I train and I go back home.
"I am always at home. Yesterday my family and friends were there and I left.
"The most important thing is health.
"If we are in good health, life is not bad. It's a difficult day, we've reached the final and we're still working."