You should eat less greasy foods. It seems to be a build up of fat.
It could just be a swollen lymph-node.
Swollen lymph node, often from infection. Nothing to worry about. Give it a wk or two. . The Internet is no place to diagnose medical problems you are having. If you are worried you should go and...
That is your mastoid bone. Or at least it should be.
Just wait for it to go away.
this is probably a cyst and should be looked at by a physician