Friend came over and literally shook my head
 

I've been doing alright recently but haven't been able to tolerate head bumps well over the past few years.
I was at a concert last night and randomly saw some friends. One of them, I guess forgot about my head issues so when he walked up he grabbed my head and shook it back and forth for a second. Really surprised me and I've had a minor head ache ever since. One of my friends even commented on how violent it looked. I'm a little concerned now about what kind of damage that could have done.

He did not do any damage. He may have strained your neck or upset your vestibular system or just caused a bit of a relapse due to previous issues.

If you look for symptoms, you will find them due to the power of suggestion. If you just ignore the situation, you will be much better.

No matter what, you cannot change what happened. You can only change how you respond.

Whether or not you think your friend should have remembered, he had no responsibility to remember about your condition. But, he should never be grabbing anybody and shaking their head. The neck is just too vulnerable to subtle injury. Being at a concert put you at risk of being jostled. If you do not think you can tolerate being jostled, you should avoid those environments.