Posture corrections must.

Have you been taught any stretching or strengthening exercises by the Physiotherapist? Are you continuing those exercises? As your diagnosis says it's a muscle spasm, and your nature of job is a desk work for long hours, you should continue with your exercises regularly.

Need proper treatment for same. Use pain'relieving gel like volini gel or diclofenac gel. Use ice pack or hot water fermentation three times 10-15min. Start doing exercises for neck and shoulder. Strengthening exercises for shoulder. Stretching for neck like trapezius, levator. Pectoral stretch.andvwall pushup nerve stretching. Isometric exercises for neck as well. 10 rep with hold counting 20.

These are usually postural pain related areas. And these problems are multifaceted. Factors could involve: Spinal rotations, lack of strength in key muscles, degenerative joint disease related pain, sheuermanns disease, neck stiffness, rotator cuff  weakness, nutritional deficiencies Vit D and B12 etc.... A posture brace is never an option usually. But maintaining good flexion/extension and rotation is important. Also maintain good movements in the neck and lumbar spine (surrounding areas) So to sum up it can be hard to deal with postural pain. However if it is a single factor pain it can be easier to address. So I suggest visiting other locations, get an overall idea on self management. It go for maintaining movements

Since you mentioned that it started after workouts at the gym there could be a possibility of - micro tears in your muscles around the shoulder blade which lead to stiffness as a result of healing by adhesions - muscle imbalances of the shoulder and shoulder blade (scapula) giving rise to trigger points, tightness and pain. ( ROM of shoulder is not significantly altered because the scapula and it's muscles compensate) - tendinitis of the rotator cuff or rhomboids - thoracic spine joint stiffness and postural syndrome due to prolonged sitting w.r.t your professional life.

Hi As per your writing and the prescription you attached shows it as a muscular pain and tighthness over your right side neck , shoulder as well as your shoulder blade. This usually happens when one does gym with weights and fluctuate with the weights. One more possibility is that it might have worsen with your job as your profile shows you are a IT employee and due to this lockdown you might be working from home which also adds up to the pain and tightness because of wrong posture. But nothing to worry , it will go off if you do follow few steps.