They were made to pay for their ineptness in front of goal when Darel Russell headed home from close range in injury time to make the final score 1-1.
Stimson said: "We had some great opportunities towards the end and we needed another goal to kill them off.
"I thought early on we could not get near them and you could see what a good side they are.
"With the penalty we got lucky - it was a 50-50 decision and you just have to get on with it. But after that our decision making was poor and we got punished."