The incident took place last evening when the girl had gone to relieve herself at a jungle in Incholi area here, a police spokesperson said.
The girl snatched the knife from the accused Raees (23) when he attempted to force himself on her, and attacked his private parts with it.
Villagers arrived at the spot after hearing his cries and admitted him to a hospital, where his condition is stated to be serious.
Police said they have registered a case against the man after a complaint by the girl.