'Workaholics' Blake Anderson 911 Call -- 'Stabbing Pain Around Anal Area'

"Workaholics" star Blake Anderson seriously injured his anal area last month when he jumped off his roof onto a beer pong table -- this according to the 911 call placed the morning after the stunt gone wrong.

As we previously reported, Blake fractured his spine during the accident -- which occurred at a raging house party at the actor's L.A. house in December -- and he subsequently required back surgery.

According to the caller -- Blake's dad -- Blake plummeted 20-25 feet during the fall, adding, "He landed on his feet but now he's having extreme pain around his lower back area and his buttocks ... to the point where he can't walk." His dad clarifies, "There's a stabbing pain around his anal area."

The dispatcher asks how Blake fell -- and Blake's dad blatantly lies ... claiming the actor "stumbled."

But as you can see in the video, Blake did NOT stumble -- Blake took a flying leap off his roof while the crowd chanted, "Blake! Blake! Blake!" He then crashed, ass first, through a beer pong table.