The lump under your ear lobe is in all possibilities an enlarged lymph node
. The fact that it is very tender to touch and that you had fillings done to your teeth a week ago implies that the dental procedure has resulted in this enlarged lymph node. Some degree of dissipation of bacteria into the bloodstream can occur during a dental procedure and this can lead to an enlarged and tender lymph node. I would suggest that you check with your dentist
regarding the requirement of any antibiotic at this stage and also if additional procedures are necessary.