That's a braze-on peg for a frame pump, and will not affect the fork in any way. Steer tubes for 1" threaded and 1" threadless forks are the same diameter, so the protrusion won't affect your ability to mount a threadless system if you choose to go that route. The steer tube doesn't actually touch the inside of the head tube, but rather is contacting the bearings/cups of the headset a few mm inside the head tube.