The carotid artery pain in left side of neck means (if this is the case) that there may be carotid artery disease which is when the arteries that supply the brain (its front) with oxygenated blood, get narrowed. There are two such arteries that go at the either sides of the neck and their pulse can be easily felt right under the jaw line.
So why do the arteries narrow?
The main cause is the buildup of cholesterol and fatty plaque along the inside walls of the blood vessels. Such narrowing makes the blood transfer more difficult, which results in higher blood pressure, larger artery size and the lack of enough blood to the brain, putting you at risk of a stroke.
Why one can get such a terrible disease?
The main reason is an unhealthy lifestyle, which includes a poor nutrition (along with bad eating habits), lack of physical activity, diabetes, bad habits such as smoking, and a family history of the same disease.
Another unpleasant thing about this condition, is that it may lead to the development of arteriosclerosis, which is a chronic disease, when the wall of carotid arteries get harder and thicker, thus losing their natural elasticity. This again results in a poor blood circulation to the brain. The bad thing about arteriosclerosis is that you cannot find the obvious cause of it.
When the carotid arteries get dilated or distended the carotidynia occurs. It has 3 types: classic, migrainous and arteriosclerotic, and all of them lead to pain in left side of neck, as well as to face, head or ear pain. The same is true for the pain in right side of neck due to carotid artery disease.
What to do with the pain in the left side of neck because of the artery problem?
There are many treatments available; but you need to get diagnosed to determine the right one for your condition. Surgery is a serious step in treatment and it won’t be takes, if the artery blockage is less than 50%. If there is carotidynia, the treatment involves the use of anti-inflammatory medications to relax the arteries.
More things to consider
Some people say that if there is a sharp pain in left side of neck, but no symptoms have been observed, than it might be a temporary thing. If the pain shoots to the head, then you need to check it out as soon as possible.
For temporary neck pains in the left side a cup of hot coffee in the morning can help (you get a pretty quick relief, but it usually lasts for half an hour). If it is due to the neck muscle spasms, then Ibuprofen may help.
You can read more about carotid artery disease here.