The girl was sleeping outside her house when Sonu took her to a field and raped her on Saturday night, they said.
He then fled the spot, leaving the girl writhing in pain, they added.
When the girl's family found her missing after the midnight, they started a search and found her in the field, police said.
An FIR was lodged yesterday and Sonu, who has over a dozen criminal cases pending against him, was arrested, they said.