The incident took place on Tuesday morning and the minor victim was identified as Navya Prakash Sonawane, police said.
According to police, the minor boy was behind the wheel at the time of incident, while car driver Mohammed Amar Chaus, was seated beside him.
The deceased, Navya and her three-year-old sister Sayali were on their way to a temple along with their uncle, Shirish Sonawane (35) when they were hit by the car near the Hudco TV Centre chowk, senior inspector Pratap Baviskar of Cidco police station said.
After the accident, an irate mob roughed up the suspects and tried to burn the car, but the police intervened and brought the situation under control.
Sonawane and his niece were admitted to a private hospital.
The minor boy was detained, while Chaus was arrested in this connection, police said, adding that the incident was captured on CCTV cameras.