I know how it is once you spot a spec of dust or any slight fault inside a watch. You then notice it every time you look at it...
If you can't ignore it and as it is (if I recall correctly) a 2003 model, it might benefit from a service if not already done recently.
Personally I would recommend Steve Burrage at Rytetime. I sure he would be very familar with the 7750 movement.
Dave