Chris Brown -- Accused of Assaulting Girl Inside Nightclub

11:20 AM PT Chris just scoffed at the allegation, tweeting, "I didn't do anything."

Chris Brown has been accused of badly injuring a 24-year-old girl inside an Orange County nightclub Saturday night ... and the alleged victim says it was so violent she might need surgery.

Deanna Gines tells TMZ ... she was in the VIP section with Chris at Heat Ultra Lounge in Anaheim -- where he had just performed. When the bar was about to close, she claims Chris shoved her to the ground. Deanna tells us, the shove was deliberate and she fell hard on her knees.

Deanna tells us she filed a police report, and a rep for the Anaheim PD says a female did indeed file a report for assault inside the club, but the rep won't disclose the name. Cops are investigating.

Deanna says she went to the hospital and doctors told her she had torn ligaments in her right knee. She's going to see another doc later this week and she says she's already been told she may have to go under the knife.

Chris Brown's rep, Nicole Perna, tells TMZ, "I'm unaware of the incident, as is Chris' lawyer and his entire team. He was in a great mood after Powerhouse." Perna adds, "None of this makes sense."