Making the Diagnosis
A simple sniffle isn't usually a matter for the doctor. You can easily diagnose a cold yourself. After all, you've probably had it enough times.
Many people say they have the flu (influenza) when really they have a bad cold. The flu can be easily distinguished: it causes a high temperature and muscle aches. Real flu doesn't usually cause a blocked or runny nose.
It's important that other conditions such as "strep throat" or bacterial chest infections are not passed off as being "just a cold." If you start developing symptoms that aren't typical of the common cold - like coughing up thick brownish sputum or getting a high fever - you might have a more serious infection. In this case you should see your doctor.