The Cameroon international was dismissed for a stamp on Robbie Blake and compounded matters by refusing to leave the pitch and throwing his shirt on the ground.
He told the club's official website: "I was frustrated after the penalty and I was being fouled, but my reaction was bad.
"I know I should not have behaved like that, it was wrong.
"I also say sorry to the manager and my teammates because now I can't help them in the second leg.
"I understand that I was wrong and I will learn not to act like this again."