How can I know if I have a swollen lymph node or a paraganglioma below the ear lobe. The swell is about 3cm and it doesn't hurt. I have no infections?

Lymphadenopathy. You need to have yourself checked by your doctor and you need cbc. No neglect as some serious diseases can be cured if diagnosed early.
See doctor . The doctor should be able to tell the difference between the two entities.