You may be able to sand that.
If you use Silicone, the drain will be there for 20 years or so. It's not like you would have to worry about it.
I suspect I already know the answer to this question, but ...
I have an American Standard sink with what appears to be a casting / finishing issue on the bottom surface of the sink where the drain hole is formed. It appears there's a bubble or void in the surface that allows water to leak past the rubber spud washer on the bottom of the pop-up assembly (the washer extends about half-way between the hole and the edge of the surface). Is a replacement sink the only "correct" solution, or can this defect be sanded out or otherwise dealt with? I don't relish the idea of gooping this up with silicon or plumber's putty as that seems like a hack.
This is an undermount sink that was attached by the counter top fabricators so it will likely be a bit of a pain to pull it and replace it.
AS quality control does it again...
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013
You could probably use something like JB Weld to create a new level and smooth surface.