In South Africa, flapjacks are what we call crumpets. (Well, we also call crumpets 'crumpets', but that's another story). I can understand the naming of the flap-necked chameleon, but I can't really figure out why they call
Chamaeleo fuelleborni a 'flapjack' chameleon...
Anyway, mysteries aside, growths can be quite serious and can be the result of any one of a number of problems.
Could you post some pics, and provide more detailed information about your husbandry? That would make it easier to diagnose any obvious problems.
(Read the sticky in the health forum:
How to ask for help)
It would probably be quite prudent to take him off to a vet. Even though he is eating well now, and looking healthy, that could change at any moment if there is something wrong with him. Chameleons hide their illnesses well, usually until it is too late.