I think you're pretty brave giving the bike 'what for' without knowing the cause! I'm sure you would have mentioned any unusual vibration, but it looks like deformation. Is it in the same spot - relative to the valve? Have you got the facility to deflate the tyre completely (with it off the ground) and press the tread with your thumb to feel for any soft spots?
Simple really - visited a nice smooth section of tarmac close to home, paid particular attention to how the front end felt, stopped and checked the area of the tyre that was of concern. There being nothing untoward I gradually upped the pace and pretty soon was up to speed. Stuish and Blade Runner 1 had it pretty much spot on, the mark was from the bike being parked on the concrete garage floor with hot tyres.
That's a relief that it's not a tyre issue. I misread your original post & thought it occured on two different surfaces! D'oh.
