? Lymph node
It is not feasible to provide a meaningful opinion without taking additional history, and physical examination, however your description suggests an enlarged lymphnode.
It may be due to an infection in your mouth or on the scalp. You may watch and wait.
You may feel the node every couple of weeks, if the lymph gland doubles in size, becomes painful, ulcerates, or other nodes become enlarged, or you develop fever
, you should see a doctor.