Tom Nichols fired a stoppage-time winner to give Peterborough a 2-1 comeback victory at Bristol Rovers.The striker was left with a simple finish from eight yards after substitute Gwion Edwards had got past Tom Lockyer to deliver a low cross from the left.Rovers had taken a 57th-minute lead when Matt Taylor hit his 11th goal of the season from the penalty spot following a foul by Shaquille Coulthirst on Dan Leadbitter.Coulthirst made amends five minutes later, firing home the equaliser from close range after Michael Smith's effort following a calamitous error by Rovers keeper Kelle Roos had been blocked.Roos spilled a straightforward cross and his mistake turned the game.Rovers had the better of few first-half chances, top scorer Taylor seeing a low 40th-minute shot deflected narrowly wide.Luke McGee made a diving save to deny Charlie Colkett, while Rory Gaffney shot too close to the Peterborough keeper from a good opening just before the interval.Posh's best first-half effort was a low 25-yard drive by Nichols after he turned his marker on 23 minutes, but Roos saved, diving to his right.