The accused Vishal Bhalerao committed the offence on November 6 when the victim's mother was not present in the house, Assistant Police Inspector (API) M M Jadhav said.
The boy also threatened her to not reveal the incident to anyone, he said.
When the girl's mother confronted him, the accused threatened and abused her, the official said.
A case has been registered under relevant sections of the IPC and under the Protection Of Children from Sexual Offences (POCSO) Act, he said, adding efforts are on to nab the absconding accused.