Do you use Gabapentin for migraines? There are lymph nodes behind the ears so finding one that is hard (not soft and spongy) needs to be checked by a M.D. as soon as possible.
That lump could be anything from a cyst to cancer you should make an appointment with your doctor & let them see it & decide what's going on it could be what doctors call a fibroid cyst what that does is it starts off small gets bigger then dissolves it is harmless & won't have to be removed. But without going to the Doctor you can't really tell.