It was the first event of the Winter Olympics in Sochi – ahead of Friday’s official opening ceremony.
“My dream was to get to the final, I’m so happy to make it in my first Olympics”
“I can’t believe what I’ve done,” said Nicholls, who was seventh after the first run but scored 86.75 in the next round to move up to fourth.
Team-mate Billy Morgan was sixth but has another shot at qualification via Saturday’s semi-finals.
Slopestyle is making its Olympic debut in Sochi, but much of the pre-event talk has focused on the controversial course.