'Jersey Shore' Ronnie Ortiz-Magro Files Battery Report with Police Against Jen Harley

Ronnie Ortiz-Magro has just gone to cops and filed a police report against Jen Harley, after she allegedly threw an ashtray at his head ... TMZ has learned.

As we reported, Ronnie and Jen got into a big fight shortly after midnight at a Las Vegas New Year's Eve party at the Hustler Club, and that's where she allegedly hurled the ashtray in his direction, striking him and cutting his nose, lip and forehead. When Jen got home, she found someone had ransacked the place, smashing a flat-screen TV and a vase. They also destroyed pictures and glass frames.

She called the cops and claimed Ronnie was the culprit. Cops named Ronnie a person of interest.

As for Ronnie's police report, we're told his motivation is that he wants Jen to get professional help. He's also worried about the safety of their 8-month-old child.

We're told Ronnie took photos of his injuries and submitted them to cops. We're also told cops took additional pics Thursday at the police station because the injuries were still visible.