Sounds like you strained a facet joint or two. The fastest treatment would be mobilization ... I'm a big fan of Geoffrey Maitland's techniques. You can look for someone trained in his methods
here. Osteopathic treatment or chiropractic would work too.
If you want a do-it-yourself approach ... get out your lacrosse ball and start rolling that whole area. Do levator and upper trap stretches. Focus on your posture by sitting/standing as tall as you can. Do upper cervical nodding exercises (low effort to recruit postural muscles only).
HTH,
