I have exactly the same condition on my steering wheel, and I too have not scratched it nor harmed it in any way.
My dealer, BMW Gallery in Norwell, MA is taking care of it, agreeing that it is a warranty issue, although no one has any idea why the situation is now appearing, about six months after being delivered. (They are positively fantastic both in sales and in service, by the way.) We are now waiting for the new wheel to arrive from Germany.
Good luck having your problem addressed!