Lymph on right side of face under ear.

Hi.  I have a soar lymph node under the ear on right side.

I have been to the dentist and although i do have  slight problem with a filling on that side, that needs to be replaced, the dentist does not see any association with it.

Xrays of teeth show nothing. 

ENT doctor has had me on 2 different kinds of antibiotics and still it is sore and slightly inflamed.

Ears, nose throat all clear and not sore.

CAT scan and CT scan show nothing but slightly enlarged.

Blood test shows liver and kidney function o.k. 

Any suggestions on what this could be.

I am at a loss.