Wolves boss Kenny Jackett let rip at referee Bobby Madley after his side had a strong spot-kick appeal dismissed in the early stages of their first away defeat of the campaign.
Madley, taking charge of his first match since awarding Stoke a controversial late penalty in a recent Premier League match at Swansea, refused to point to the spot despite Posh defender Mark Little appearing to handle Bakary Sako's cross.
It proved to be a pivotal moment in a match settled by a single goal - a free-kick from Posh skipper Michael Bostwick with 11 minutes remaining.
Ferguson said: "The game was never going to be a classic and it was all about getting three points.
"We produced a brave performance and hopefully the result can bring the belief and confidence flooding back.
"We don't get enough joy with our free-kicks and Michael should take more of them.
"We know what he is capable of doing in those situations and it was a goal worthy of winning any game."
Bostwick lashed a 25-yard strike past Wolves keeper Carl Ikeme as out-of-form Posh snapped a five-match losing streak in League One in style.
That was the hosts' only on-target effort of the afternoon, but Wolves had also created little in front of goal.
Wide man Sako fired one decent opportunity into the side-netting before testing Posh keeper Bobby Olejnik with a smart volley in the second period.
Leigh Griffiths and Danny Batth also squandered good headed opportunities as Jackett's men failed to find a breakthrough.