What happens next?

How to get pen stains out of clothing
Buy a stain remover meant for ink stains.
Look in the laundry aisle at your local grocery store or shopping center and see if you can find a stain remover that says something like " removes ink stains " or " eliminates pen stains " on it.
Blot the ink stain using a damp cloth before you apply the stain remover.
Try to lift as much of the ink stain as you can using just the cloth. Apply the stain remover to the pen stain.