By all accounts the Latics were never even in the game at the City Ground as Forest comfortably ran out 3-0 winners.
The result pleased new manager Freedman, but the gloss was taken off the by the injury sustained by Assombalonga.
The striker is believed to have suffered a dislocated knee cap after slipping whilst shooting in the second half.
Freedman said: "We don't know exactly how bad it is yet, but he will go for an MRI scan in the morning. Then the doctor will give me his opinion on what's happening. He will get a second reading and will let me know by Friday.
"He slipped as he went to shoot and his knee gave way on the grass. We're looking at least a few weeks, but we don't really know.
"I felt it dampened the crowd a little bit and both sides went very null and just wanted to finish the game. I was, though, so pleased for the fans that saw a convincing win, three different goalscorers, a clean sheet and a committed performance."
The result was Freedman's second win in as many games since taking over from Stuart Pearce as manager and he added: "As a coach, I am very pleased with what I have seen. The players have taken things on board and they are very committed to the team ethic. We are going to try and build on these results and performances.
"We have to make sure we keep winning games of football now, although I admit that we won't win every match."
The result lifted Forest up to tenth place, twelve points off a playoff place,