Brighton looked set to take all three points after Jake Robinson's goal but were denied even one after two Grant Holt strikes.
McGhee told his club's official website: "We need a bit more - we've lost the game and we can't argue with that.
"But for long parts of the game we were the best team."
McGhee also felt his side were unlucky to concede the penalty that brought Forest back into the game, calling it a 'soft' decision.