Swedish defender Olsson was unlikely hero for the Rams, curling home the only goal to settle a scrappy match with just over 10 minutes left.
The 27-year-old told BBC Radio Derby: "The atmosphere was unbelievable
"I have heard about this game so much so to have scored in it is amazing. What I have heard is what I witnessed."
Derby remain fifth in the Championship table, but January signing Olsson is well aware that his first goal for the club - in his ninth game - had more significance than a 'normal' goal.
"To score a goal in such an important game means a lot to a lot of people; it's a very good feeling," he added.
"It was a good finish. We didn't play our best football but sometimes it is about grinding things out. It's a good win."
Derby County match-winner Marcus Olsson says his first experience of a facing Nottingham Forest in the A52 derby lived up to all the hype.