Well, I can't say for sure without putting my hands on the tire, but it doesn't look like it's dimpled in the tread groove, which makes me want to say it's just in the tread surface and probably nothing at all. But don't take that as gospel; I'm just looking at a couple internet pics. I would guess it might've been an irregularity when the tread surface was manufactured.
2011 Victory Cross Roads, crimson red
"There is only one God, and His name is Death. And there is only one thing we say to Death: 'not today.'"