The Hammers meet Forest sitting inside the bottom three and having lost at bottom-of-the-league Wolves on the weekend.
On the Wolves defeat, Nuno said: "We’ve analysed and looked at it, and it was bad. We started badly again, and we didn’t do the things that we should have.
"If you go back, with the way we were performing and the ideas we were putting across, everything came down in ten to 15 minutes. We’re disappointed about that, because if you compare it to the previous games, it was bad."
Nuno continued: "We are worried and we are concerned, but the good thing is that we have a game tomorrow to put things right.
"We have to perform better and make better decisions. Everything has to be at maximum focus, but the good thing about football is that you always have a chance, and we’ll be doing everything we can to get the right result.
"Every game is very important, so we have to approach tomorrow in the same way. We know it is a very, very important game.
"Forest are a good team, full of talented players and with an experienced manager, so we know it’s going to be tough."