The 23-year-old fell badly on his left leg when challenging Antoine Semenyo after just six minutes of Saturday’s 1-1 draw with Bournemouth at the City Ground.
Danilo had nine minutes of treatment on the pitch and was taken to the Queen’s Medical Centre in Nottingham. He will be assessed further on Sunday.
“It was a horrible moment for everybody, he has broken his ankle,” said Nuno.
“It’s serious, we are going to miss him, not only on the pitch. He is a wonderful boy. He is always smiling, always with joy, and we wish him the best.
“Everybody loves him so much. He is leaving hospital just now and he is going to be assessed tomorrow. It is serious but the good news he is stable. He’s speaking and aware, he just needs time.”
When asked how long Danilo may be out for, Nuno added: “I cannot answer that, I just wish it is short, he is a very important player for us.”
Following Danilo’s departure on a stretcher, Forest took a 23rd-minute lead through Chris Wood only for Semenyo to equalise with four minutes left.
“It (Danilo’s injury) stays in the head of the players but the response was good,” said Nuno.
“It was a good game, a tough game, both teams had chances, controlled the game, had momentum. In the second half we had possession, good combinations and we conceded in the last minutes. We are disappointed about that.”