hello and welcome to Health care magic,
I am Dr Sriram Nathan and I shall try to help you out with your problem
The swelling behind the ear since is of a short duration can be due to many causes most of which are benign and harmless so you do not have anything to worry about.
Since it hurts then you may also have an infection in the area. Try an antibiotic like the amox-clav in consultation with your doctor. You may also need pain killers for your pain and may be even injection for better symptom control.
You may start a course of anti reflux medication
, along with an antihistamine like levcetrizine. Your doctor will know about these.
get a dental consultation and see if there is anything like a jagged teeth which is irritating the area
Take only non spicy, non oily and warm food and fluids
Take a course of multivitamin
in consultation with your doctor
If you do not get better in a week or so then you must consult an ENT doctor who may advice further course of action which may include endoscopy
and may be even biopsy
to get a better picture
take care and do not worry
Dr Sriram Nathan