Woke with a stiff neck. Couldn't turn to the left even a 1/2 inch without using hands. Painful. Had complete mobility to the right. That lasted 24 hours. Had almost complete mobility to the left the next day with little reminder pain. Noticed slight cold/numb feeling in right foot and it has since spread to encompass the ankel, shin,and thigh (not groin just front to outside to center back thigh). Through it all I have had use of both arms with no pain.
The big question is whether there is any connection between the stiff neck and your cold leg. I suspect they are two disparate conditions.
Is your leg actually cold to the touch? If your spouse compares the legs, are they different in temperature? If so, it's a vascular condition and you shouldn't delay, get to your doctor immediately. It could be a clot, or a condition called claudication, an aneurism... don't delay.
You don't give your age, but if you are elderly, it's possible you have "cervical stenosis' a narrowing of the spinal canal in the neck that can affect the spinal cord and cause bizarre conditions in the lower limbs. It's not common.
Then a most uncommon brain condition when one of the cerebellar tonsils descends into the foramen magnum causing both neck and distal problems. That is VERY rare, but should be kept in mind.
All in all, I would begin with a good medical examination. Today.
Let us know what transpires.
Dr. Barrie Lewis