© PA Photos
David Nugent soon restored Leicester's advantage, but Cox's spot kick in the second half earned his side a valuable point.
Leicester got off to the perfect start after six minutes when Lloyd Dyer made inroads down the left to cross for Forest defender Ward to divert the ball into his own net.
Anthony Knockaert could have doubled their advantage moments later, but his free kick was saved by Lee Camp.
The visitors equalised midway through the half when Cox reached the byline before pulling the back for Guedioura to fire home from eight yards.
Forest were level for just 10 minutes before Leicester regained the lead, when Nugent deftly flicked the ball over the advancing Camp from 12 yards.
Forest pulled level for a second time midway through the second half when Sharp was brought down by Zak Whitbread in the penalty area, and Cox stepped up to send Kasper Schmeichel the wrong way.
The equaliser failed to discourage Leicester from attacking for the three points, with Dyer seeing a goalbound shot blocked.
Waghorn was then denied twice in quick succession, and despite a final push by the Foxes, they couldn't breach Camp's defences for a third time and they were forced to settle for a point.