Does not appear to be standard rail wear, but rather looks like a piece of debris was caught in the rail and chunked out that bit.
If you can get a fingernail and it feels rough or raised to the touch, I would consider using a very small file or fine sanding stone to smooth out that area only - not beyond the gouge, just the raised or rough area.
Otherwise, keep it thoroughly lubricated. SIGs tolerate semi-indifferent maintenance, but will work better and have greater longevity if you are diligent in your cleaning and lubricating routine. Anything short of dripping out of the rails is fine, lubricate the rails with grease just short of the point of making a mess.