It sounds like it may be an infection but here is something you can try for a day or two to see if it starts clearing up the eye problem.
If it hasn't helped in that time, then it isn't likely that it will and a vet visit will be needed so he can get antibiotics to get cure the infection and to protect his eye from getting permanently damaged by the infection.
It's important to have him treated by a vet who regularly treats chams--or at least plenty of other reptiles.
You can rinse your cham's eyes with a gentle saline solution,several times a day which may help him to get the irritant out of his eye.
You want to gently squirt the saline solution into the eye and fill it up so the lid puffs out temporarily.
Even with closed eyes the gentle stream can penetrate the closed lid.
I've used these for eye rinses
http://m.cvs.com/mt/www.cvs.com/shop...jtt_v_menu=exp
AND have also used this one by Bausch and Lomb
This Bausch and Lomb solution is made with the same ingredients called Sensitive Eyes Plus
http://m.cvs.com/mt/www.cvs.com/search/_/N-0?pt=global&searchTerm=Sensitive+Eyes+Plus&un_form_encoding=utf-8&un_jtt_searchCVS.x=19&un_jtt_searchCVS.y=10
You can also cut and paste the questions from
https://www.chameleonforums.com/how-ask-help-66/, then add all of your answers, so we can see if anything might be causing your cham to get sick.
Very often people are given incomplete care instructions or wrong care instructions, so then the cham doesn't get everything he needs to be healthy.
Like other creatures, this isn't always the cause of illness and sometimes they get ill for unknown reasons.