The on-loan striker from Southampton took his tally to eight goals in 18 games and was also at the heart of the flashpoint incident that Warnock felt swung the game in Forest's favour.
Leeds were ahead through an 11th-minute goal from Paul Green but Sharp went down under a challenge from Tom Lees to give himself the chance to equalise from the spot before the end of the first half.
Sharp then fired his second of the game soon after the restart and a three-goal blitz in nine minutes - Rodolph Austin scored a clumsy own goal and Dexter Blackstock headed home the fourth - stunned the visitors, who had a late consolation from Davide Somma.
"I just hope Tom learns from the incident - it is a harsh lesson for him but one he's got to make sure doesn't happen again," he said.
"I've known Billy a long time and if you are up against him in the area he's going to be clever. Tom has just breathed on him but Billy has made sure there is contact and gone down.
"In that situation you have got to stand a yard off him.
"It's a penalty because 20 out of 20 referees would give it. Billy used to get penalties for me like that at Sheffield United so I can't complain. Tom has just got to be more professional."
Forest parted company with boss Sean O'Driscoll following the game.