It's cold, and my calf bones ache faintly.

There are several possibilities: first, the measures to keep the calf from cold are not in place, and the cold invasion leads to a dull pain in the calf bone. Second, suffering from rheumatism and rheumatoid diseases. It may cause dull pain in the calf bones. Third, the muscles, nerves and bones of the calf have been accidentally injured, and may also be attacked by cold and moisture, resulting in dull pain in the bones of the calf.