Sydney boy punches attacker and flees

A teenage boy has punched a man who allegedly indecently assaulted him at a sports field in Sydney's northwest before racing home to tell his mother.

The 14-year-old has told NSW Police he was indecently assaulted by a man in his early 20s, who had a husky voice and was wearing a black hoodie, outside a Kellyville sporting field on Thursday night.

The teenager punched the man and ran home where he reported the incident to his mother.