Welcome to the forum!
Lathis offers good advice.
Jackson's are from rather humid areas and need proper humidity to shed .
Looking at your picture, linked below, I believe it's just some scales left from a shed.
It also looks like he would benefit from some extra misting time each day.
Too often, sellers don't really know chameleon care and they don't realize that Jackson's need higher humidity and longer mistings than many other types of chams.
Many people buy automatic misting systems like the MistKing or Aquazamp to ensure that their cham gets frequent, long enough mistings to drink and humidify the enclosure.
In general, Jackson's like cooler temps and higher humidity than other chams, plus they need less D3 and multivitamin supplements than many other types of chams (Panther, Veiled).
Here is an excellent caresheet that was written by the forum moderators about Jackson's and their care
https://www.chameleonforums.com/care/caresheets/jacksons/
The picture can be seen here
http://s44.photobucket.com/user/torreyakatoe/media/imagejpg1_zps1567d80f.jpg.html?filters[user]=141165970&filters[recent]=1&sort=1&o=0
I just love Jackson's and am glad to help fellow Jackson's owners.
(I've also bred 2 of mine and have a couple of their youngsters for sale in the Classifieds.)