Nintendo aware of Switch playtime glitch, will share more info soon

If you were worried that your total Switch playtime is gone forever due to the recent glitch, you don't need to worry anymore. Nintendo is aware of the issue and is planning to address it soon.

"Some Nintendo Switch owners' play activity information is displaying incorrectly. We are aware of the issue and we expect to have more information to share in the near future."

from GoNintendo