The Brazilian thought he had won the match for his team when he netted in the 80th minute, but the Portuguese outfit conceded a last-ditch goal to Luka Zahovic.
"We showed that we are an inexperienced team and that costs you in the Champions League," he told reporters.
"Experience can make a difference, like with what happened, but this is also part of football. It is good to learn from it and I'm sure that we will improve in the next game.
"We showed character on the pitch and we played a good football team. Of course we have to correct certain defensive frailties, but we must hold our heads high and keep working."
Nani's goal against Maribor was his first since joining Sporting from Manchester United.