Canaries goalkeeper John Ruddy blasted against Nathan Tyson to concede a freak goal after just three minutes, but Grant Holt responded with his 20th goal of the season and Andrew Surman completed the comeback.
Lambert said: "That was a massive win, as big a result as we have had all season. Forest are a good side, as good as we have seen down here all season, and made it very difficult for us.
"They got an early goal and put us under a lot of pressure in the first half but we hung on and got ourselves in front and played exceptionally well at times. We also showed a great desire to go out and win the game. Everything you need to do to win a game of football was there in abundance.
"I'm delighted with the players. They have been absolutely brilliant, especially when you consider they have had to play three games in six days. They'll be playing seven in a month and that seems absolutely ridiculous to me it's far too many, but that's the situation and we've got to get on with it.
"Basically I can't praise the players highly enough. They've been absolutely colossal for me again and they deserve all the praise that comes their way."
Source: PA
Source: PA