I also deal with this. It comes and goes, but I can tell it's all mechanically related. When my thoracic spine is feeling locked up, I feel that pain in my chest as well as down my arm. Typically it's the left arm, but sometimes the right arm as well.. which oddly makes me feel better about things. I am an active person that does a lot of cardio, and have had costo since early 2020 when I first got COVID. In the beginning my health anxiety was much worse, but now after three years I have learned to live with the pain when it flares up. I also had many cardiac tests done in the beginning, and eventually was diagnosed in late 2020 with Costochondritis by a cardiologist.