Lohan suffered cuts and bruises in Tuesday's accident. She told authorities she would get treatment on her own, police Lt. Ted Matthews said. Police had previously said the 18-year-old actress-singer was uninjured.
Matthews said Galo Ramirez was in a van following Lohan, apparently to get a photo, when the actress spotted a police vehicle going in the opposite direction.
Lohan was trying to reach the police vehicle to report that she was being pursued. Ramirez then intentionally rammed the left rear of her 2005 Mercedes-Benz, Matthews said.
"That obviously got the attention of the black-and-white unit," he said.
Ramirez, 24, was arrested for investigation of assault with a deadly weapon and released on bail.
Lohan "was shaken up and extremely upset" after the crash, a spokeswoman for the actress said Wednesday.
Matthews said there are a lot of close calls with paparazzi chasing celebrities to photograph them. "This guy just carried it over the line and ran into her."
Last year, Lohan starred in "Mean Girls" and released a pop album titled, "Speak." Her new film, "Herbie: Fully Loaded," will be in theaters June 22.