The ink rub should not be the concern, especially a small one like that.
The Mylar inner well that is slowly almost guaranteed to create waves in the book at some point in the future should really keep you up at night.
Many months ago when the new case released the inner well that holds the book in place was made up of two pieces of Mylar.
The Mylar sandwiched the book in place creating a floating effect.
Unfortunately this had some negative side effects that CGC addressed and has since been replaced by the classic tried and tested inner well.
Not sure where on the forum you would be able to look this up because most of the threads and posts related to this issue where erased from existence.
I would look up CGC creep engine or newton rings CGC case and see for yourself.
I am not sure if CGC will reholder the book at no charge but that is something they were doing when the old inner well was brought back.
I would call and find out because the inner well your book is in has been known to cause damage.
Best of luck and for future reference when buying books with the new holder design, try to make sure it has the old inner well
Examples of old inner wells in new CGC holders.
Left one is the casket design and the right is envelope design. (These are not official terms)
You can see around the left edge of the book that it is like a casket, used on thicker books.
There is also another kind of inner well that does not have the casket corner and is more like an envelope, a design better suited for thinner books.
It can be identified by the white line that goes around the book, as seen in the right image.
Hope this description helps.