I have had a large size bump on the back of my head.  I went to the doctor when I first noticed it in 1983, he said not to worry that it looked to be a assist bump. If it does not get any bigger or have any pain not to worry.  Now, it has become liquid in form, redness and discomfort when I lay my head on the pillow.  Can you tell me anything based on what I have told you about it?
Hi, dear. I have gone through your question. I can understand your concern. You may have some Desmond cyst or some other cystic lesion.  If it causes pain and discomfort then you should go for removal of that lesion. Just consult your doctor and plan for surgery. Hope I have answered your question, if you have doubt then I will be happy to answer. Thanks for using Chat Doctor. Wish you a very good health.