After quiting any habits, withdrawals symptoms usually occurs like ulcers and all.
Because of smoking
the mucosa ( underlying soft tissue ) of chhek is burnt results in white lessions called sub mucous fibriosis which in turn causes burning sensations while eating.
But as you have left smoking 2 years back these ulcers can't be withdrawal symptom hense its some
other factor causing ulcers which can be identified only by clinical examinations.
Please visit any dentist
specially Oral & Maxillofacial Surgeon for further investigations....