Nottingham boss Steve Cooper said giving up a late goal is the worst way to lose.
“Especially having fought in the game. We came up against a really good team and we knew it would be like that, possibly,” he said.
The result left Forest 14th in the standings, two points about the relegation zone.
“When you are in the position we are in, every point is vital,” Forest midfielder Jonjo Shelvey told Sky Sports.
“The way lads dug in deep, we deserved something from the game. But it wasn’t meant to be. We dust ourselves down and go again.”