Hello and welcome to HCM,
on the cheek may have multiple reasons,you may have cheek bite caused by sharp cuspal edges of molar teeth that often leads to white patches on cheek mucosa. This can be minimized by selective grinding of the sharp edges professionally by your dentist.
Deficiency of cretain vitamins also leads to tissue ulceration.
White patches are also initial sign of tissue necrosis
eventually growing into a cancer, habits like tobacco chewing
,smoking,alcohol,hot and spicy food habits are responsible for such patches.
i suggest you to consult a dentist
and get it confirmed,meanwhile you rinse your mouth with lukewarm saline or chlorhexidine
mouth wash regularly, apply topical oral ointment like Mucopain over the affected area, start with antioixidant course of Lycopene 2000mg along with multivitamins twice daily for 10 days. i hope this helps you to recover soon. take care.