A Cervical rib (or a 'hypoplastic cervical rib') is an extra rib that can be present in about 1 in 200 persons. The rib may be present on one side only but sometimes on both sides of the body. The rib is present just behind the collar bone at the top of the chest wall near the neck and is diagnosed by Xrays. You can see a picture of the rib here:
Most people with a cervical rib may have no symptoms at all and the rib may be diagnosed only on Xrays for some other cause. But in some cases, the rib can decrease the space required for the passage of nerves and blood vessels from the chest ('thorax') to the arm on the same side. This will cause pressure and pinching of the nerves- there will be pain, tingling and numbness and weakness of the arm. The condition is called Thoracic Outlet Syndrome. You can read more about it here:
If the symptoms are severe enough, surgery may be need to cut away the extra rib. Otherwise, physiotherapy is usually enough to take care of the condition.
I hope this helps.
If the symptoms are due to the presence of the cervical rib and physiotherapy has not helped, I am afraid there will be no option other than to cut away the rib by surgery. This is not a very major surgery , though, and should not be much trouble. You will feel much more comfortable later.