My daughter woke up complaining that the back of her hear is sore . she is 4 years old. what could this be ?

Lymphadenitis: A tender lymph node may indicate inflammation or infection. Please check her temperature, and watch for redness, swelling and pus. A middle ear infection may also present with pain around the ear. Provide fluids, place a cool compress on the area and use children's Tylenol for pain, until see by your pediatrician. She will possibly need a course of antibiotics, have a flu vaccine.

Ear pain: Ear pain (or pain behind the ear) can be caused by several things. She could have a middle ear infection or a swimmer's ear. She could have a bruise if she got injured. If she doesn't have a fever or isn't acting sick, you can watch her for a day or so. If she acts sick, see her doctor to check it out. Not all ear infections need to be treated with antibiotics.