Brief Answer:
Infection a possbility
Detailed Answer:
There are many causes for this.
You have nodes related to infections under the jaw line. Hence, these could be related to infection. Any infective process leads to enlargement of nodes. It could be acute infections like
aphthous ulcers, injury in the face with infection etc wherein the nodes would be tender to feel. It could be chronic infections like
tuberculosis etc wherein it may be non- tender.
Non infectious diseases like
sarcoidosis etc can also cause nodal enlargement.
As you have presumed, cancers can also cause nodal enlargements. It could be a cancer of the lymphoreticular system affecting the nodes itself or it could be elsewhere spreading to the nodes. your symptom of
fatigue could be related to that.
It may not be a node at all. Generally swellings in that area are lymph nodes. However, as a rare possibility, it may be something else like a fat tumor (
lipoma) etc.
As you have rightly understood, you have to see your doctor for diagnosis. But since you are otherwise asymptomatic, I feel that the chances of cancer are less.