The distribution of your symptoms on the left correspond to the opthalmic branch of the 5th cranial nerve (i.e. the trigeminal nerve). This nerve supplies sensation to the face, including the eye, and the top of the head. We have one on each side.
This nerve is commonly irritated and can fire inappropriately causing pain or abnormal sensations known as paresthesias. When pain fibers are involved, it can cause a very uncomfortable condition known as trigeminal neruralgia. When non-pain fibers are involved (including the temperature fibers) the sensations are not necessarily painful but very annoying, and sometimes downright distressing. They include numbness, tingling, cold or heat sensations, even a sensation of "insects crawling" across the skin.
Problems with this nerve are more common in migraine sufferers, so the condition is probably related to your optical migraines. At any rate, a normal MRI essentially rules out a mechanical cause (e.g. tumor, stroke). This is true for the vast majority of such cases. While the exact cause is usually not found, most cases resolve over the course of several weeks to months, once the nerve calms down.
In the meantime, you could ask your doctor about using a nerve-stabilizing medication such as gabapentin, pregabalin, or carbamazepine to calm the nerve and expedite its return to a more normal state.