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A concert worker says he's physically disabled right now now now ... and it's all Akon's fault -- after the singer allegedly stage dove right on top of the guy, causing him permanent injury.

A man named Matthew Graham has filed a lawsuit against the singer, claiming he was working Akon's show at BayFest music festival in Alabama back in 2009 -- when Akon "negligently or wantonly leapt into the overcrowded mass of concertgoers" and struck him. See video below (scroll to 00:50).

Graham says he sustained severe and permanent injury to his knee, back, head, and body during the incident -- and is now physically disabled. He doesn't specify the extent of his disability.

Graham is suing for medical expenses, lost wages, physical pain and mental anguish -- demanding unspecified damages. He is also suing BayFest, Inc.

Calls to Akon's camp weren't returned.