I tweaked the muscles in my neck/upper back. Do I apply heat or cold?

I took a red-eye flight and was sleeping in an uncomfortable position and tweaked the muscles in my neck and upper shoulder. I can’t really move my head right now. Yesterday I applied heat to it and took 2 advil and it got better throughout the day till I barely noticed it at night. Then I woke up this morning and it was much worse. My mother is telling me to apply cold first and then heat, but the cold on my muscles feels worse. Any opinions? And yes, I know I should see a physical therapist but I’m traveling and will be on the road for a week. I need a quick fix because I have important meetings for work and can’t go looking like an immobile robot.