PLEASE HELP my chameleon puked up a whole worm and some cricket matter

[Klyde O'Scope]

is this possibly fatal or can I somewhat relax and not worry.

I'm not a veterinarian, but I'd say we're at the "wait & see" stage.
Concern: yes. Worry: no.
IME, worry accomplishes nothing except stress; it is not constructive for either the worrier or worryee.

 

[dinomom]

is this possibly fatal or can I somewhat relax and not worry.

As Beman said, no need to worry until you see if it repeats.

That said..impaction can cause regurgitation in almost all animals; do you have substrate, moss or plastic plants in the enclosure?

Also has he had a nice poop lately? Constipation can also be implicated.