What you describe could be the symptoms of inflammation in the base joint of the thumb. I would recommend you make an appointment to see your doctor as soon as possible to get it checked out - there are many possible causes of such pain or inflammation (if indeed it is inflammation) and it's best to get it checked out by a medical professional. Until you see your doctor, to get temporary relief, take ibuprofen and try applying an ice pack to the area that's hurting - if you don't have an ice pack, get a bag of frozen peas, wrap it in a dish towel and place it on your thumb.  If that doesn't work, try heat - some people react better to ice, some react better to ice.