New signing Britt Assombalonga's goal after nine minutes proved to be decisive for the Posh.
Ferguson told reporters: "It was a great start, clean sheet, with the new boy scoring a goal to win us the game. I thought first half we were very good, we should have been more than the one up.
"Second half we tired a little bit and they got control of the game, but in saying that I thought it was a bit harder than a should have been towards the end. The boy Ryan Mason hit the pair but apart from that I thought we looked solid.
"All you can ask for in the first game really is to get a win, there's definitely room for improvement but it was a solid performance and a good win."
Peterborough were one of seven sides to start the new League One campaign with maximum points.