What you were told sounds appropriate. One of the symptoms of PCS is muscle tension/spasming. One may also experience postural rigidity where the postural muscles, back, shoulders, legs etc. go through a spasm or momentary stiffness. I tend to do this rigidity tensing with my shoulders and especially my latissimus dorsi (Lats), the muscles under the arm pits. I also do it with my abdominal muscles, sometimes in conjunction with holding my breath.

There are various ways different people experience these stress behaviors. Learning to recognize the situation and relax to relieve it will help.

I would not worry about it. Worry/anxiety is the likely cause so additional worry/anxiety will only make it worse.

My best to you.