Do you have discomfort also in the back of the thigh?
Or into the bottom of the foot?
Any back pains?
Is this calf swollen, or red?
OK.
This is only in the calf muscle, not the shin?
And it doesn't come on or worsen when walking long distances?
This is a bit tough to figure out, as it only seems to affect a certain portion of your leg, yet not radiate elsewhere, and have no other specific symptoms.
But from what you are saying, the sensation of pain along with cold (altered temperature sensation) often relates to nerve irritation.
But there are two major nerves that affect the lower leg, one for the front (shin) area, and one for the back (calf) area. Regardless, they could be irritated / inflammed and be the reason for your symptoms. The lack of redness and swelling make things like a blood clot less likely, and the fact it doesn't worsen with walking make blood vessel and other nerve compression - neurogenic claudication - unlikely.
So, while this may be irritation with a nerve, it may resolve on its own, but if it doesn't certainly having a doctor examine it in person would be best, since there really is only so much that can be done over the Internet.
Doctor (MD)
U.S. Physician/Surgeon in Neurosurgery