i have found a small knot on the back part of my head just about where my neck and head meet. it started on my left side about 5 months ago and now has moved to the right side and has slightly moved upward. it doesn't hurt at all but i get migraines all the time that usually last about a week. i've taken medication for the migraines but it doesn't help. should i be concerned of is it just something that is normal??? please help???