In this case, put a tennis ball inside the socks and hang it over your shoulder
. Ball should be over your upper back or lower neck or wherever it pains and hold the other end of the socks with your right hand.
Now lean against tge wall and press your back against tge ball. When you roll all over your back, some points will be oversensitive and tender. Sustain the pressure at those points.
Along with that do the stretches for the levator scapulae ,trapezius, rhomboideus.
Find these stretches from the internet.
Ice compression can also help you reduce the spasm.