Had sore throat, runny nose and temperature for 2 days. not taken any medicine. now have diarrhea. are they related? do i need to contact my doctor?

Cannot diagnose: The two issues may or may not be related, but the symptoms are generally resolved spontaneously with time. Should they persist beyond several days, then yes, you should contact your local doctor.

Can b viral syndrome: Usually common this time of the year, when anybody can catch a common cold (usually caused by a virus) the virus can also affect the gut causing diarrhea, rest, fluids, and Acetaminophen would suffice, it resolves spontaneously in few days, but if symptoms get worse, fever doesn't subside with medicine in correct dosage, medical attention should be sought.