Is the pain in my side a PMR symptom?

If the back pain is due to inflammation then the Pred. will very likely have eased it ( one of the bonuses of taking steroids! ) but that does not necessarily mean that the pain is part of  PMR.

What other pains did you have before diagnosis? Shoulders, hips, legs,  in most cases bilaterally, are very common though there is nothing precise about PMR.  What was your starting dose and  how long before it relieved the pains?

You can ask your doctor what s/he thinks, of course. My PMR was first diagnosed as OA the pain of which was wonderfully relieved while on steroids. I've been off now for nearly five years and the OA pain is back with a vengeance.

Hope all goes well for you. Keep coming back.  Someone will always be around with help/ advice/ sympathy.

Perhaps not directly - but one cause of such pain is myofascial pain syndrome which leads to trigger points forming in the muscles on either side of the spine, in the shoulders, about rib level and in the lower back where the baby's dimples are. They can be felt as hard knots of inflamed muscle fibres and can irritate nearby nerve, leading to referred pain including round into the ribs. The trigger points are concentrations of the same cytokines (inflammatory substances) as PMR and at higher doses of pred they often improve considerably. And myofascila pain syndrome often occurs alongside PMR.