A lump underneath the ear could mean a lot of things, most commonly an enlarged lymph node
or a lipoma
(collection of fat globules). Best option for you to do is get it checked out by a surgeon to see what it is. And maybe even to do a Fine Needle Aspiration Cytology/Biopsy
to find out the exact nature of the lump. Then to decide whats needs to be done next.
Better get it checked out rather than ignoring the lump or worrying about it.