I had a tender spot in the same area you described a few weeks ago. I'm pretty sure mine was from massaging the area, though, so I felt better about it knowing that was probably what it was from. It went away after a few days.
I've had headaches most of my life, so I'm not overly concerned when I get them (I had extensive allergy testing, MRI, CAT scan, you name it when I was in my early teens & they couldn't find anything wrong with me.). I'm now in my mid-30s & do worry about brain tumors at times. But I do think it's just part of the anxiety, as in the last several months I thought I had a heart problem (strained chest muscles from an injury -- all cardiac tests came back perfect), a blood clot in my leg (pinched sciatic nerve -- x-rays came back normal), and so many other things. I constantly think about having an MRI done to check my head, but if it came back normal, would I just move on to the next worry?
Anxiety is such a pain in the ass. It causes us to lose so much precious time. It makes me sick to think of how much time I've wasted worrying over the last several months. And yet there's still that annoying, 'but what if my body is trying to tell me something is wrong?' voice. Ugh. So here's what I keep trying to tell myself: If there's bad pain or a real worry about something, I need to have it checked out. If for nothing else but peace of mind. Otherwise, I have to IGNORE whatever it is & WAIT. If something lasts a week or more (depending on what it is), then I should get it checked out. And you know what? Usually within a few days or a week, whatever it is gone. Obviously, if you're concerned that it could be a life or death issue (like when I worried about my chest pains & having a numb leg), get it checked out. It's not worth the agony of worrying yourself over. I know if I hadn't gotten help either of those times I wouldn't have been able to sleep. And God forbid it was something serious. But all these little things that come up for me are usually explained pretty easily (like right now, my seasonal allergies are kicking in, which would account for my head discomfort at times), or they go away after a few days.
In your case, the dizziness could absolutely be from anxiety. I sometimes have dizziness with my anxiety. (My seasonal allergies were also causing my ears to clog up, which I believe could also cause dizziness.) And tension headaches could also be from anxiety. After decades of suffering from tension headaches, I realized mine are almost always related to muscle tightness in my neck or shoulders. And when you're worried about something, those are often areas that tense up.
For my sake, I'm not even going to Google vertebral artery dissection because then I'll probably think I have it.
So I can't give my opinion on that, but maybe try to tell yourself what I'm trying to tell myself. I feel for you.