The Toon were 4-1 ahead at halftime before Forest fought back in the second-half.
Nuno said afterwards, "First half, clearly Newcastle better. Second half was better but unfortunately not enough. Too bad, too soon.
"It's about trying to settle down, calm down and try to be ourselves. In the first half I didn't recognise our team. In the second half we were much better.
"I don't know, this is what I'm going to work on now. This is a game which is good to reflect on.
"We made mistakes. Newcastle made mistakes also. But it was two totally different halves. We started well, we scored, and they just rolled over us.
"There was nothing else in the first half about us. Every time Newcastle had the ball they scored.
"I wish there was 10 minutes added on. We needed that time. We were on top, Newcastle were on the ropes. With 10 minutes I think we can get something from this game."