Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain and explanation of symptoms it seems that he has some disorder related to the submandibular salivary gland as diffuse swelling below the cheek under the jaw bone is mostly due to it.. In case if there is no pain and discomfort associated with it it can be most probably any blockage in the salivary gland or its duct due to formation of crystalline stones from the minerals present in the saliva and when the saliva does not efficiently flow from the gland to mouth the saliva flows back into the gland and cause swelling.. You should consult an oral physician and get evaluated and a clinical evaluation and a CT scan can help in confirming the diagnosis as few other conditions like lymph node enlargement,dental abscess or salivary gland infections etc can also be a probable cause of swelling in that area.. Any treatment can be planned once the diagnosis is confirmed.. If you need further queries you can follow up on Healthcare magic with pictures and investigation reports.. Hope this information helps.. If you find the answer helpful please give me a Five Star Review and click on found the answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora..