What Causes Frequent Migraines While Having Linear Indentation On Right Skull?

I am 60 years old and have frequent intractable migraines since 1996m and have not worked since 1999. I am in fair health otherwise and have not ever smoked. I had a my thyroid removed 2 years ago due to multiple large and growing nodules. I am on 75mcg of levothyroxin. A couple of months ago, I noticed my skull, at the crown, had an round indention, approximately quarter-size, with slight pain when touched. Now, in the indention is another indention the size of a finger print. Oh, it started with a linear indention on the top-right of my head where I had a hit it in an auto accident. The bump grew immediately after impact, but was completely gone within 3 hours because I had put an ice pack on it within ten minutes. A few months later a slight linear indention showed up on the top-left of my skull. The largest and deepest is the one at the crown. Thank you. Ann