Dear Goatgirl,
It is not typical for chest pain to occur with exercise. Ordinarily, the majority of pediatric chest pain is not because of a heart-related reason. However, when it occurs with exercise, it should be taken more seriously. I would start with your pediatrician and have him/her obtain a history and examination. If this remains unclear or worrisome, you will likely be referred to a pediatric cardiologist for further evaluation. Most likely, since this is exercise-related chest pain, a pediatric cardiology evaluation will be necessary. Typically, an electrocardiogram would be a first test that would be performed. However, without all of the history and examination information, I cannot recommend which testing needs to be done outside of this.
Great news--I'm glad that he is well and has no cardiac disease.
Thank you so much for responding to my question. I followed your recommendations and took my son back to see his pediatrician, who then referred us to a pediatric cardiologist. We saw the pediatric cardiologist last week and thankfully all is well with my son. The doctor said the pain he was experiencing was just growing pains, most likely caused by under developed pectoral muscles (since he was able to reproduce the pain during our visit) and not anything heart related. They did do an electrocardiogram on him as well just to be sure and that too was normal. Thank you again for your advice.