That small of a dent will have no effect on your pipe performance, but if you're like me, just seeing it everyday makes it look a whole lot bigger than it is. Some people use air pressure to bring out the dent and there is a way to do this in 2002 editions of DirtBike magazine. Carefully following this procedure could get the dent out, but small deformaties as the one you describe are difficult to deal with. You could drill a small hole in the center of the dent and pull it out ala body shop fender repair, or maybe a dent puller with a suction cup and adhesive would work. Were it me, I'd probably jsut get used to it and live with it.