Persistent right side chest to arm pain for 8days. ecg normal, muscle pain killers/creams not helping. sometimes pain is on left side. what is this?

Many possible: diagnoses could explain your symptoms. At your age and sex and with a normal EKG and with the pain migrating it is unlikely to be anything serious. It is most likely musculo-skeletal. Potentially blood clots, bleeding or systemic inflammatory diseases could cause your symptoms. It would seem reasonable to get checked out by a health care professional.