You probably did irritate the neck & surrounding muscles by slouching and possibly tilting to relieve pressures?
Did you use a cane or crutch on the one side at all?
That could affect the body too.

The muscles may be spasming and compressing on the nerves a bit.

As long as you don't have any serious cervical spine issues, some heat or ice if that feels best for you , gentle stretches and range or motion movements are good to do.

If it is really painful ask for some phys therapy to get things back on the healing track.

posture is a very important thing