She took to micro blogging website Twitter to announce the news.
"I am not part of Khatron Ke Khiladi Darr ka Blockbuster due to fracture. I have broken my toe finger in three pieces. Thank you all for the love and support," Mahhi posted on Tuesday.
A source close to the show also confirmed the news.
"Mahhi had hurt herself last week and was still contemplating on joining the show. However, she will not be a part of the show now," the source said.
The other contestants in the show are Ranvir Shorey, Gauahar Khan, Kushal Tandon, Mugdha Godse, Rochelle Maria Rao, Nikitin Dheer, Dayanand Shetty, Salman Yusuff Khan, Pooja Gor, Rajniesh Duggall, Gurmeet Choudhary, Debina Bonnerjee and stuntwoman Geeta Tandon.
They have left for South Africa, where the show will be shot, on Tuesday night.
Khatron Ke Khiladi Darr ka Blockbuster will be hosted by director Rohit Shetty and will air on Colors.