<s>[INST] i just found a small lump on the mastoid bone behind my right ear. it seems to be connected to the bone and it doesnt move. i would say its about the size of an eraser on a regular pencil. it only hurts if i put pressure on it. im an 18 year old female. im concerned as to what it could be. what do you think? [/INST] Hi. Thanks for your query. The lump of the size of the rubber eraser on the pencil, which does not move and tender only on deep palpation, and is situated on the mastoid bone is a lymph node unless proved otherwise. You can get an FNAC. See for the Dan Chat Doctor.  These lymph nodes are very resistance to get regressed fully. If you are too much bothered you can certainly get this removed and send it for histopathology examination. </s>