Carbaryl is not commonly used on tobacco. Here is a vegetable pre-harvest interval.
https://www.gardentech.com/blog/how-to-guides/harvest-with-sevin
If you used dust or liquid, then hose the plants, and wait a few days to a week before you harvest. If you've already harvested the leaves, they I suppose you'll need to wash them, then hang them out in the sun for a few days.
A safer choice for next year is to either pick off the hornworms by hand, or purchase a BT (
Bacillus thuringiensis) spray, which is harmless to all but caterpillars.
Bob