Hornworms tend to pick a spot on the leaf, hold on with their back legs, then swing their front end while munching. (At least, that's how they teach them to do it in hornworm school.) As a result, they usually cause damage in curved lines, rather than the jagged profiles I see above. Also, the small ones tend to avoid eating the secondary veins. If a hornworm starts feeding on a tobacco plant, it usually stays on that plant until it's large enough to be easily spotted.
So I would guess it's not a hornworm. Most mammals avoid tobacco, once they recognize it. But those unfamiliar with it (young rabbits, groundhogs, livestock, etc.) may munch on it for educational purposes--leaving random chunks missing. Grasshoppers and crickets will sometimes eat young tobacco, though they seem to avoid it, once the nicotine levels rise. Slugs might cause that damage, and if occurring on many nearby plants, would prompt me to put out Sluggo or beer traps.
The punchline: Some of my plants of about the same age show nearly identical damage. It's in very widely separated locations. I just ignore it, rather than lose sleep. Those lovely bottom leaves will end up as fliers and trash anyway.
Bob