Firstly he need a simple chest X-ray ,just to see if it is of a bony origin or not.If there is pain,it almost always indicates that there is an inflammation process going on. Yes,he should get it checked by the doctor.Fine needle aspiration cytology (FNAC) may be done.In this technique, a thin, hollow needle is inserted into the mass/lump to extract cells that will be examined under a microscope. based on this the exact diagnosis can be made.
The various possibilities are:sebaceous cyst,haematoma,ganglion,callus formation malignancy,some types of infection or inflammation.The exact diagnosis can only be made after clinical examination by the doctor & FNAC as required.
Hope my answers had helped.