The incident took place last on Tuesday last week when the Constable Vilas Shinde (50) from Bandra traffic division was discharging his duty at a petrol pump when he spotted a biker without helmet approaching the petrol pump.
The juvenile was nabbed by police in the late hours on the same day.
Shinde who was in a critical condition and was unconscious since last week, passed away at the Lilavati Hospital on Wednesday afternoon, police said.
The biker had indulged in a verbal argument with Shinde when he was asked to produce vehicle documents and the license. The biker then phoned his friend who arrived at the spot within minutes and joined him in the argument.
The biker then banged a wooden plank on Shinde's head, after which the duo fled the place, while Shinde was rushed to Lilavati hospital by his colleagues.
Terming the constable's death as a 'sad' incident, Mumbai Police Commissioner Datta Padsalgikar said, "Vilas Shinde was assaulted while he was doing his duty. It's very disheartening, if such incident happens during course of duty.
"I pay homage to the departed soul. Our heart goes out to the family member of the deceased," Padsalgikar told reporters.
Chief Minister Devendra Fadnavis met the family of Shinde in Mumbai on Wednesday and promised all possible help by state government.
He assured a job to a family member of the deceased and also financial assistance.