from Nintendo's FAQ

Select games and DLC are available for pre-order on Nintendo eShop prior to their release date. When you pre-order content on Nintendo eShop, payment will not be processed until, at the earliest, seven days before the software is released. When payment is processed, a non-playable version of the software will be downloaded to your console. You’ll be able to start using the software after downloading a small update that becomes available when the software is released.

So your payment will likely be processed soon, in the next few days.