What you are describing sounds like costochondritis. It isn't necessarily related to PMR but it is possible.

"Examples of health conditions that can feature costochondritis include fibromyalgia, psoriatic arthritis, ankylosing spondylitis, reactive arthritis, rheumatoid arthritis, lupus, and inflammatory bowel disease (such as ulcerative colitis and Crohn's disease)."
https://www.medicinenet.com/costochondritis_and_tietze_syndrome/article.htm
I had PMR as an add-on to reactive arthritis. I often had flares of costochrondritis when it hurt to inhale every time I took a breath.