Goals from Charlie Lee and Chris Whelpdale helped the home side narrow the deficit between themselves and the Foxes to four points, but Pearson is now encouraging his side to get their title challenge back on track after the setback.
"Peterborough were the better side and there are no complaints from me about the result," he said.
"It is obviously disappointing to be beaten and the result will undoubtedly create plenty of interest with Peterborough cutting the gap at the top.
"It didn't happen for us and Peterborough have to be given the credit for playing well and getting the momentum behind them.
"We had some key players missing but that is not something than can be used as an excuse. We now have to concentrate on making sure we do enough to keep our position at the top."