City won 2-0 at Wembley on Sunday through goals from Rico Lewis and Josko Gvardiol.
Nuno said afterwards: “We started the game really bad. City started really well. When you concede the first chance, it makes everything hard.
“It took a little time to feel comfortable and adjust. After that, we did a good game.
“The first half was more difficult. Second half, the momentum changed a little bit and we had a couple of chances which could have put the game in a different story.
“Overall, the hard work was there and the commitment was there. The boys gave it their all. We must accept we lost but recognise that we worked very hard."
Forest players not overawed
Asked if his players froze on the day, Nuno insisted: “No, I don’t say that. I say City created a lot of problems, especially when they are in front on the scoreboard. How they keep the ball and try to unbalance you. it is not easy.
"Today, it's a sad day. It's going to be hard. But tomorrow when you wake up and the sadness is gone, we are going to know we have big things ahead of us to fight for."
The Forest manager added, “We always learn from the games - individually, as a team, as a club. As a club, today we have learned it’s possible to achieve what we want to achieve.
“We are very thankful for the way the fans stayed until the end to applaud us. We cannot thank them enough. We keep going."