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.
However, Warnock believes the penalty marked the start of his side’s downfall.
“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.”
Substitute Nathan Delfouneso struck deep in stoppage time for Blackpool to deny Huddersfield a first win in eight games as an entertaining npower Championship clash finished 1-1 at the John Smith’s Stadium.
Anthony Gerrard’s first goal for the club looked to have ended Huddersfield’s barren run but the Seasiders were excellent value for at least a point.
The visitors bombarded their opponent’s goal for an hour, but a combination of bad luck and poor finishing looked like giving the Terriers a first clean sheet since their last victory against Barnsley back on November 10.
Blackpool should have been out of sight by half-time, with the home side unable to find a method of breaking up their stylish attacking play.
Bradford City kept up their good form thanks to another late winner from super-sub Alan Connell.
Connell headed home Kyel Reid’s cross with four minutes left.
The Bantams went ahead in the first half when Garry Thompson tucked away a knock-down by James Hanson.
Stanley looked like they had earned a point when Rommy Boco levelled from Luke Joyce’s free-kick on 79 minutes, before City struck late on.
City stay in 5th, three points behind 3rd-placed Cheltenham and with a game in hand.