Although pleased with the overall outcome, the assistant manager was disappointed with the first half when his side could easily have found themselves behind despite Stevie Hammell's early own goal.
William Gros, who had earlier made three goal-line clearances, deservedly scored the clinching second goal before Motherwell's frustrations got the better of them in the closing minutes, with first Fraser Kerr and then captain Keith Lasley shown straight red cards for wild tackles on James Dayton.
Nicholl said: "We had a great start to the game and although we were lucky to get the own goal I thought `here we go'.
"Then we did nothing except face waves of attacks from Motherwell when we just couldn't get the ball out of our own half.
"I said to the players at half-time that they didn't have a chance of winning the game if they continued like that - and I`m sure they were sitting in the Motherwell dressing room wondering how they weren't ahead.
"We took off (Borja) Perez to try and get a grip of the game and I think we need to praise the players for defending and taking their chances, and having the game won before they had two players sent off."