The incident went down at Box Nightclub, where she held an event Saturday night to launch her new fashion line, River Island.
About 3 a.m. on Sunday, according to the Daily News and Daily Mail, Rihanna was leaving the venue with friends Melissa Forde and Cara Delevingne when the heckler began yelling at her about Brown. The heckler then threw a bottle of Lucozade, a British energy drink, at the 24-year-old singer.
She dodged the bottle, and in the chaos fell against a metal shop gate and cut her knee, according to reports. Photos show her dabbing at the blood.
Her bodyguard also injured his leg amid the chaos and had to be taken to a hospital for treatment, reports the Daily News.