I would google 'exercises for trapped nerve in neck' and it should bring up Youtube videos for you to watch and copy the exercises.
eg.
https://www.youtube.com/watch?v=TffT8b3Ych4I have Ulnar Nerve Entrapment and copied the exercises from Youtube and they did work.
I would think your headache is due to the neck nerve as I have arthritis in my neck and shoulders and can get a headache from it.
I would also recommend a memory foam pillow which is what I use as it helps your neck align properly as you are sleeping.
I would also recommend one of those wheat bags that you heat up in the mircrowave for 3 mins then wrap around your neck.
Hope you get some relief so you can enjoy your holiday.