Hi and thanks for your question.
I would suggest maybe suggesting to the doctor you need a more deeper evaluation, I think you won t refuse it from you. Tenderness on touch could suggest inflammatory diseases. However the pain could also be a referred by actually coming from another organ like an abdominal region.
I chest X ray
is very important in reassuring that there is no imminent chest organ structure lesion or damage.
I suggest a proper examination and chest X ray be done first, to exclude these serious conditions before attributing the pain to heavy load lifting.
Thanks hope this helps,