Hirani, 52, has been admitted in the Intensive Care Unit (ICU) of the Lilavati Hospital in suburban Bandra after he fell off a motorcycle.
"He is in the hospital... He is in the ICU. He is fine and there is nothing to worry. He will be discharged soon shortly today," Dr Jalil Parkar from Lilavati Hospital said.
"Hirani's jaw is dislocated and fractured for which doctors operated on him," he added.
According to sources, one of Hirani's employees had purchased a new motorcycle and asked him if he wanted to ride it.
The 'PK' director agreed and was driving at a low speed, but could not manage the bike's weight and fell.
The director, screenwriter and film editor is best known for the movies 'Munna Bhai MBBS' (2003), 'Lage Raho Munnabhai' (2006), '3 Idiots' (2009) and 'PK' (2014).
All the films directed by Hirani went on to become huge successes at the box-office.