Hello and welcome to HCM, A lump at the base of skull and behind ear could be due to lymph node enlargement. Lymph nodes at base of neck drain the back of scalp and neck. Any infectious focus at nape of neck and back of scalp can cause enlargement of these lymph nodes. Painful lymph node enlargement suggest an acute infection. However, a clinical assessment is required to ascertain the nature of swelling and its probable origin. I suggest you to consult your physician for clinical assessment. An aspiration cytology of the swelling may be done wherein a needle is inserted into the swelling. The aspirated cells are spread on a glass slide, stained with appropriate stain and examined under microscope. The nature and character of the swelling can be determined by aspiration cytology and thus further management can be planned. Thanks and take care Dr Shailja Puri