The three youths, who were sitting in the bus, started passing lewd comments against the woman. When the boy opposed them, he was assaulted by the accused.
Irate locals blocked the road at Ramchal Chowk to protest the incident.
Meanwhile, police have registered a case against a police inspector for allegedly harassing a woman police constable.
SP city Sarvankumar said that a case was registered against Ranvir Tomor?with civil line police station and an inquiry is on.
The inspector has been shifted from control room to another place.
The woman costable had accused the inspector of misbehaving with her.