Does it look/ feel like big deep ridges vertically along the piston? Do the rings look like they`re being held in by the scuffing?
If it seems like it was running okay before you noticed this, I would guess that it`s not that bad.
I think I would at least take the offending cylinder off & inspect it. You can leave the head in place, saves you a head gasket. You may even be able to re-use the base gasket, though it will probably need replacing.
You`d be suprised at what you can clean up from the piston and cylinder.
Have you got much experience of pulling engines apart?
If you`ve only just got the bike (from Fastline)? Perhaps you`ll want to try getting them to fix it under warranty?