I have hard big lump on neck behind ear?

See Head & Neck doc.: Possible lymph node vs. parotid gland mass other rare cause. Enlarged nodes from 1) normal response to inflammation 2) lymph node cancer 3) regional cancer moved to lymph node 4) weird infections. Parotid masses usuallu require surgery but 80% are benign. If this has been present for more than a few weeks please see a doc experienced in head and neck disease. Usually a Plastic Surgeon or ENT.

Lymph node: Probably a lymph node. Whatever it is, you need to see your MD.