Thanks for writing to the forum!
Well, the lump could be a lymph node, a neurofibroma (localized harmless swelling in a nerve) or a lipoma (localized collection of fat). Folliculitis (hair follicle infection) can sometimes persist. It can also be acne.
Hope this helps. It is difficult to comment beyond this at this stage. Do consult your doctor. Please let me know if there is any thing else and do keep me posted. Take care!
Most lumps in that site are due to infections or benign tumors of soft tissue origin. Behind the ear there is skin, fat, cartilage, bone, nerves, blood vessels, Lymph nodes, and salivary gland tissue (a portion of the parotid salivary gland extends behind the ear). A bump can develop from any of those structures, and could be due to a tumor (benign or not), an infection (Lymph node or skin), a swollen muscle or salivary gland, etc.
My suggestion would be to wait it out for a few weeks to see if it changes in size. If it gets smaller, it was nothing. If it happens to get bigger, then make an appointment with your doctor.You may take some pain killers or some anti-inflammatory drug if you have pain.
Hope it helps.Take care and pls do keep us posted if you have any additional queries.