As the other member mentioned, keep your hand at a distance. Don't get so close that he puffs up. He will come to you once he decides to eat the food in your hand. It takes practice, sometimes a lot depending on your Cham. There's probably some videos on YouTube. I do recall one in particular where a guy was feeding fruit and veggies to his Cham. You might want to start off with worms. Once he gets used to eatin those out of your hand, anything else will be a walk in the park. Just don't put your hand right in front of his face. Have it to where he can see it, and walk towards it. Be slow and don't jerk if he gets too close. My Veiled likes to get really close to my hand before he shoots his tongue out. Greens are easy, but fruit (such as strawberry and bananas) tend to not stick to his tongue well. I think I started cup and hand feeding when he was about 3.5 months old. By the time he was 4 months I started feeding vegetables. The older they are, the easier it is in my opinion. But you also want to start when they are fairly young, but not too young. Just try to find some videos, and practice. Not every Chameleon will hand feed, but the majority of the forum members have been successful.
One other thing.. I've left very small pieces of Kale scattered on Bodhi's vines before and he ate a lot of it. But that was a little after he ate it from my hand. You could try that instead of huge chunks. Although I'm afraid he might not be enticed because he doesn't know what it is yet.it could be worth a shot though. Just let him see you placing it in spots around the cage. An keep it in one general area. You never know.