The 29-year-old was with the rest of the film's cast when someone from the crowd threw a stone Monday.
She took to Twitter to share her angst, and wrote: "A stone was thrown at me on stage in Faridabad, it hit and hurt my lip, for the first time in my life, I'm truly ashamed of our people."
"It's deeply disheartening to have to say horrible things about my country... but this was uncouth and had it have been someone 'more important' it would not have gone down well," she added.
According to an eyewitness, "Sarah was in tears the moment she was hit and it resulted in slight swelling. However, ice was immediately applied on the injury."
The event was titled an "adult party" and Riteish Deshmukh, Tusshar Kapoor and Neha Sharma were also on stage.
Following the incident, Sarah and Neha did not stage their performance and were sent to their van.
"The man who threw the stone could not be identified," the source added.
Sarah says though she isn't happy about the incident, it has failed to dampen her spirits in any way.
"I'm not okay but if they were trying to defeat my spirit, it hasn't worked," Sarah wrote.
"Kyaa Super Kool Hain Hum", produced by Ekta Kapoor, is a sex comedy, releasing on August 3.