If that Happens to me on an item, I cure the ring for at least an hour to make the exterior hard, then with very fine sandpaper,clean up all the lines. Then put it back in and cure some more. The reason for curing again is to make sure all the outside and inside areas you cleaned up are cured solid. You can actually polish the B9 material using plastic polishing compound.
Most of what We print at my factory has no lines or very little, It has a lot to do with orientation of the pattern on the build platform.