I am an internal medicine physician who has had migraines for 45 years or so and has been treating patients with them for more than 35 years. Here are my thoughts on the matter.
In one paper I read many years ago, neck pain was the second most frequent symptom of migraine after headache. This is very common and one I experience myself. For this reason, a lot of migraine patients are misdiagnosed as having "cervicogenic" or "tension" headaches and they are mismanaged because they aren't offered actual migraine treatment, but only NSAIDS and PT. These patients aren't here at this forum because they've not been properly diagnosed; they are at some tension headache support group wondering why their diclofenac gel applied topically to their neck isn't doing any good.
In my own experience -- and many patients tell me, too -- sumatriptan doesn't help neck pain, though it relieves many other symptoms. You're not alone in this. I find using a microwavable hot pack to the back of my neck helps. My wife used to massage my neck, but we're now elderly and her hand arthritis is too bad to do this anymore.