thanks for your query,
i have gone through your question. the cause of the mass in your cheek could be because of lipoma
or arterovenous malformation within the muscle or it can be a calcified mass within the muscle...i advise you to get an ultrasound
done in that region to rule out the above said causes... and you need to take radiograph like OPG to rule out and odontogenic causes consult your oral physician for prompt diagnosis and treatment...
i hope my answer will help you..
Dr. Mahesh Kumar T.S