Tony Hawk -- SORRY FOR HOVERBOARD PRANK .... Didn't Think People Were That Dumb

Tony Hawk is sorry ... he's sorry that some people were actually STUPID ENOUGH to believe his obviously phony hoverboard commercial was real.

Of course, hours after the video was released, it was exposed as a gag clip for 'FunnyOrDie.com" -- but apparently, not everyone was hip to the hoax.

"I wanna apologize for the hoverboard prank," Hawk said in a new video ... "I thought it was obvious it was fake but a lot of people believed it."