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The pain behind the ear is probably due to the wrong posture maintained during the sleep. A neck muscle called sternocleido-mastoid muscle is connecting the mastoid process
behind the ear to the sternum
. The sprain on the muscle could be the reason for the soreness behind the ear. The lump is the mastoid bone itself and it is not abnormal.
Use some pain relieving spray to relax the muscles and an oral pain relievers such as diclofenac
Dr. Naveen Kumar N.
ENT and Head & Neck Surgeon