Suggest Remedy For Persistent Headache

hi about three weeks ago I have headache for two days that started at the top of my neck and continued up the bottom back of my head. No pain reliever or migrane medicine seemed to do anything for the headache. The only thing that made it toleratable was rubbing the soft spot just above my neck where my neck and skull are. Then after the headache I woke up and my neck was stiff on the left side and was uncomfortable to move from side to side like when you have a kink in you neck. I rub my neck to see if I could feel any sore muscles or anything I felt a hard knot that will not move it is located on the upper part of back of my neck on the left side about a inch from my skull and a inch from my spine. I thought I was just tense and that I needed to rub it out. So I rubbed it for awhile no change and it didn't really hurt but it annoyed me and so I was always poking at it and rubbing it. All this did was make my skin sore from rubbing it to much. I also was laying on a heating pad to try and relax it and losing it up to thinking it was caused maybe from stress or and tension . three weeks later it is no smaller or softer and im a little worried tension in my neck would of loosened by now. Im not really still getting headaches my eyes just seem a little more sensitive to sunlight and bright light in general. If im in a well light room at night for more than a hrs I seem to get a little of a headache Im not sure if it is related to the knot. Can you please tell me what is the cause of this knot and what to do for it?