The striker, who has scored four goals in 11 appearances for Forest this season, will now spend an extended spell on the sidelines.
Speaking in Thursday’s morning’s press conference ahead of Saturday’s fixture against Brighton and Hove Albion, Cooper said on Forest’s website: “It’s bad news on Taiwo, he’s had to have surgery and he is going to be out for months.
“We’ll support him and try to get him back as quick and as fit as he can be, but it’s a really unfortunate situation and a blow for him.
“He’s become an important player for us with the goals he’s scored and the goals he will score for us, but he’s such a good guy and a good professional who is desperate to do well, so to get an injury like this is harsh on him.
“We’ve got to support him through the process of coming back stronger. He’s done that once before here and I’m sure he will give everything again like he did last time.