Another picture

Hornworms are the larval stage of a moth, a hawk moth to be specific - usually the five-spotted hawkmoth in the case of the tomato hornworm, though the tobacco hornworm (Carolina sphinx moth) is pretty similar. They do go through several instars, just as any caterpillar does, so they do start small. I'm having trouble seeing the details, is that a black 'horn' protruding off its tail end? Or is the dark bit nearer the leaf part of its head?

It doesn’t seem to have a protruding ‘horn’, that little dark spot seems to be feces. I came back out to get a clearer picture

Looks like an Inch Wrom to me..... still destructive.

Not a hornworm. Even in their early larval stage they are much larger than the insect shown. Agree that 'inch worm', a moniker assigned to various destructive moth larvae, is a more accurate, if non-specific ID.

Yes, that’s exactly it. Thank you :) any control methods that you can suggest? Or should I just keep monitoring and pick them off when I see them?

I always go for "pick it off" if possible. You can always spray with Bacillus thuringeinsis (Bt), which is a naturally occurring bacteria that kills moth and butterfly larvae, but nothing else. It's safe for all mammals..... and bees.