I Have A Small, Marble Sized Lump Right At The

I have a small, marble sized lump right at the base of my skull. it is painful. if i press it, it causes pain over the entire right side of my head up into my forehead. i found it about two weeks ago at the time that i began having sudden severe pain in my right arm. i could not move my arm and the pain was excruciating. i went to the er. they did not find anything. the severe pain subsided but my right hand is very weak. i can't put any pressure on it and the top of my right arm hurts. I'm not sure if the two are related. I just don't need another MD visit unless necessary because i am between jobs and don't have insurance right now.