Hi Dear thanks for question on HCM,your son is having fever
of 102 f,and has pain in left arm and feel hot .dear this pain and hotness is due to fever. your saying your son doesn't have any disease,Dear your wrong ,fever is itself sign of some under lying disease .get your son investigated for the cause of fever ,you have not mentioned age of your son .the fever could be due to many reason, at least get his CBC,URINE EXAMINATION, AND BLOOD CULTURE
DONE ,AND CONSULT SOME PEDIATRICIAN
TO INVESTIGATE THE CAUSE OF FEVER OF YOUR SON.