As we age, we sometimes get stones in the salivary glands.

This can cause a swelling on the side affected. People with dry mouth from inflammation like Sjogren's or from side effects from
drugs are more prone to this. If it becomes totally blocked, surgery may be needed. My doctor recommends sucking on a sour candy a couple of times a day to stimulate saliva production. Give that a try.

Ear infections also can do this, or a throat infection that occurs only on one side. Painless swelling should always be evaluated because swollen lymph nodes with no pain could be lymphoma.

So if it persists you really should see a doctor.