Suggest Treatment For Sharp Pain In The Head
No indication of something serious.
Detailed Answer:
I read your question carefully and I understand your concern.
Judging from the description of the pain I do not think there is any worrying cause for the it. Concerning issues such as stroke, tumors etc have constant character and location as opposed to sharp pain episodes, are not influenced at all by rubbing with Arnicare and also usually have other neurological signs.
As you yourself thought it may be related to the shoulder issues you have had. They not only may cause pain radiating in the head on one hand but as they alter posture and distribution of weight can also exacerbate neck issues with muscle spasms and irritation of the upper cervical nerves, in particular the occipital nerve. This nerve covers the area where you are having these sharp pains so its irritation is the most likely cause.
Other caused to look for would be high blood pressure, so it must be monitored during these days.
If persisting and you want to try something else apart from homeopathic measures like Arnicare, over the counter pain killers like Ibuprofen would be first option. Medication for neuropathic pain like gabapentin or pregabalin would be the next option but probably won't be needed.
If any new symptoms arise do not hesitate to write again.
Thank you! Hope you get better soon.
Detailed Answer:
Thanks for letting me know. It's reassuring that both opinions are similar. I hope you'll feel better soon.