Hmmmm ... Start off with trying Panadol (which is what the GP would advise as well, most likely.) Or Ibuprofen - but make sure you take food with it. I reckon it is Unlikely to be carpal tunnel at this stage @Locksley - most likely just a side effect of the Letrozole unfortunately. My hands were incredibly painful at one stage (particularly around the base of the thumb) - also had 'trigger finger' where one would 'lock' in the bent position & wouldn't straighten without assistance ..... I changed to Exemestane after 6 weeks & lasted 6 months on that .... then went to Arimidex & been on it for 2.5 years now, with a little discomfort but nowhere near as much as the other AIs. Everyone is different. Some hate Arimidex.
Even now, I occasionally have acute pain in the hands or feet ... but it passes ....
Keep a diary of anything 'new' happening to your body (feet & shoulders as well) and if things are escalating, get an early appt with your Onc and discuss your options - whether to try a different AI .....
I am also on the 'good oil' so I do believe that is relieving some of my symptoms, too. ;). All the best. xx