The former model joins fellow newcomers Varan Dhawan and Alia Bhatt in Karan Johar's latest production.
He told The Times of India: "One day, I was assisting Karan on My Name is Khan, and now I'm the leading man of Student of the Year. I have to pinch myself to believe this is for real.
"Sometimes, I'm a bit nervous. But at most times, I'm confident. I have landed a dream debut. Karan, according to me, has the safest pair of hands in the film business.
"I must admit that I'm a little quiet. I need to understand what I'm doing before I actually venture into it. Karan always teased me saying, 'Sid, you ask too many questions'.
"But I certainly am not the brooding type. I take a little time to open up. Karan has tweaked my film character around the way I am in real life."
Co-star Bhatt claimed that she chose to work with Johar because she did not want to make her acting debut in a film produced by her father Mahesh Bhatt.
In March, Johar said that the campus movie will be his final production featuring young people.