A good thought
Dr. Nguyen is right, a clot in a superfical or deep calf vein could certainly cause this kind of symptom. Clots might not cause anything more than tenderness and aching.
If there are anhy prominent veins, any redness and/or swelling, a clot is something you want to make sure you don't have. On the other hand, it could just be a muscle strain
. It is worth checking out.