The new mum was being tailed by a snapper as she drove through Los Angeles when he crashed into the back of her vehicle.
Richie was taken to a local hospital by her boyfriend Joel Madden's twin brother Benji, who she was spotted with soon after the crash.
Eduardo Arrivabene was cited at the scene for driving without a licence and has now been arrested for misdemeanour.
Sources tell RadarOnline.com that the paparazzo is an undocumented worker and that he tried to tell authorities it was his passenger, another snapper, who was driving at the time of the crash.
Lieutenant Tony Lee of the Beverly Hills Police says, "Ms. Richie was driving with a passenger around 2pm when she was struck by two photographers driving in one vehicle behind her.
"She complained of pain, and her passenger is transporting her to a local hospital. Her car sustained moderate damage. No paramedics were called to the scene."