Hello and welcome to the world's best chameleon forum
It's true, veiled can get very territorial and defensive, esp between 6 and 12
months of age.
It's best to leave him alone as much as possible.
When feeding, use a feeder cup, or simply turn the cricks loose in his cage
so he can hunt them down.
It's not unusual for them to zap a hand in their cage thinking there is food,
or not knowing that your fingers are not really giant worms
Try not to get your hands near him while he is in a grumpy mood, just ignore
him.
Can you please post a pic of him and your cage set-up?
You should have a cage at least 18 x 36'', and elevated off the floor, like on
a table or stand, so he is looking down on you. This makes them feel more secure.
Also, you need to have plenty of foliage, branches, vines etc. for him to hide.
They become very stressed and defensive if they feel exposed.
We have all kinds of care sheets, just scroll down and see the box on the left
that says; 'chameleon care' and click on the subject you need.
Pics!! we wanna see pics of your guy (and cage too)