Not sure if you have a wood grain or leather. Or if it was always like this within a month of getting the car.
If it's the latter, get it replaced as it is defective.
For leather, you might have had a reaction with two cleaning agents. You could try Meguiars Leather Cleaner. The hard part id determining if it is dried out or with another solvent making it sticky. If it's dried out, after a light cleaning try olive oil to rub and protect. If it's some sort of substance that has done this, try saddlesoap.
After this, if it still persists, replace, and seal the new wheel.
Best of luck!