What you are describing sounds like costochondritis to me.
https://www.mayoclinic.org/diseases-conditions/costochondritis/symptoms-causes/syc-20371175
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I had bouts of costochondritis and my rheumatoligst didn't seem overly concerned about it. I remember exactly what she said when I told her it was hard for me to take a deep breath without sternum and rib cage pain. She reassured me that it wasn't cardiac pain. She just said it comes with the territory I was in --- referring to my autoimmune disorders and "systemic inflammation." She didn't say costochondritis was caused by PMR but it occurs with many autoimmune disorders.
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The following link explains Tietze Syndrome. However, general inflammation of the cartilage in your rib cage is called costochondritis.
https://my.clevelandclinic.org/health/diseases/23565-tietze-syndrome
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You may want to discuss your symptoms with your doctor. I think it can be associated with PMR but more often with inflammatory arthritis. I was diagnosed with both PMR and inflammatory arthritis so my rheumatologist collectively called everything "systemic inflammation." I could never pinpoint exactly where my pain was ... I would complain that the pain was everywhere.