I Am Having Pain In My Left Leg--in The Calf

I am having pain in my left leg--in the calf area--it started in my foot and is now in my calf. No swelling, redness, or hurting when squeezed. Feels like a knot in my calf when I put weight on it. Pain is not bad, but hinders my walking. Seems worse at night. I'm taking Atorvastin--could that be the problem?