The 26-year-old aggravated the problem playing for Nigeria during the international break and has had an operation on the issue.
Awoniyi has scored four goals in 10 Premier League appearances for Forest this season.
“We’ll definitely see him again this season, but it’s groin surgery so it will take a little while,” said Cooper.
Former Liverpool forward Awoniyi is a key player for the City Ground side, scoring 10 league goals to help Forest achieve top-flight survival last season.
“It’s bad news on Taiwo, he’s had to have surgery and he is going to be out for months,” added Cooper.
“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. 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.”
Nottingham Forest manager Steve Cooper has confirmed Taiwo Awoniyi is set for a lengthy spell on the sidelines with injury.
The striker aggravated a groin problem while on international duty with Nigeria.
Cooper said: “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.”
The Midlands club are currently 14th in the table and must now rejig their forward line ahead of the visit of Brighton on Saturday.
Gary O’Neil has spoken about Wolverhampton Wanderers’ contract talks with Hwang Hee-chan.
Ahead of Wolves’ match with Fulham, the manager said: “I’m hopeful. There’s no real update.
“The club is in talks with Channy. I’m a huge Channy fan.
“He’s been incredible for me since I’ve arrived. His work ethic, the way he does what you ask with a smile, his grit and determination.
“Hopefully we can secure his services.”
Hwang has scored seven goals in 13 appearances for Wolves this season. His current contract is set to expire in 2026.
Vincent Kompany has claimed that he remains focused on Burnley’s own problems and has not been distracted by the Premier League’s decision to deduct 10-points from Everton.
He said: “There’s discussions at Premier League level and board level, but for one second it’s not been on my mind.
“I don’t think it is for me to make a judgement on this. I need to focus on the team and getting rewards and turning performances into results.
“Like I say, I’m aware, so not going to pretend I’m not aware, but it’s none of my concern. It’s not my job and it’s not my task.
“My task is way too important for me to get distracted by this. We are talking politics here and board-level discussions. My absolute priority is on just keeping this team in this league.
“Showing everyone we can belong here, we can be a good team in this league. None of my attention towards that case will actually help what we need to achieve.”
Bournemouth manager Andoni Iraola has spoken about Max Aarons’ recent hamstring injury and backed club legend Adam Smith to replace him.
He said: “We will have Max out for some time because he got injured in the past game against Newcastle.
“[Adam Smith is] ready to perform straight away, I have no doubts.
“Even the other day, without warming up because we didn’t expect the injury, he went straight away and nobody noticed. He was very good.
“He’s very solid, he’s very reliable. To have someone with his experience and his reliability, for a coach, is very good.”
Bournemouth are in 16th position in the Premier League and will visit 18th placed Sheffield United on Saturday.
