With 71 minutes played at the City Ground, Blues had led the game 2-0 courtesy of goals from Hayden Mullins and Marlon King but the hosts managed to claim a point following goals from Simon Cox and Dan Harding.
"A point away from home is a good result, particularly against a side of Forest's ability," Clark said afater the match.
"But when you are 2-0 up with little over 15 minutes left to play it is very disappointing to have to settle for a point.
"The players were excellent but we were guilty of dropping too deep, giving the initiative to the Forest lads and they took it.''