The 1-0 City Ground defeat leaves the champions sitting in fourth place a point ahead of fifth place Chelsea, which have played a game less.
At the final whistle, Nico told CityTV: “Well yeah, it was a really tough match, we knew it was going to be hard.
“We had our chances. We were much better than them in the first half. Second half I think it was a more open game. In the last minutes when you lose, it isn’t easy.
“Yeah I think apart from the goal I can’t remember another clear chance for them. That means we did a really good job defensively.
“At the end they wanted to keep the result 0-0 and they knew they would have a chance on the counter, or a corner, that’s why they’re third in the league and in a Champions League spot.
“It’s tough, it’s tough to accept it. But we have to keep working."
City defender Ruben Dias also insisted the players know the job that needs to be done to finish in the Champions League places this season.
He said: “Well, we’re not going to be thinking about ifs and maybes. We know our target. It is very clear.
“And we have got to push, we have got to push and we have to do our best.
“We’re not used to playing every week as well, but that is a different challenge for us.
“But we need to make it.”
Forest won today thanks to Callum Hudson-Odoi's 83rd minute strike.