Hello!
Change into comfortable shoes and rest for couple of days.
Apply ice packs and take pain killers to decrease the pain and inflammation.
Calf muscle pain is generally self induced and is caused due to too much of exercise especially related to stretching.
If your pain continues then get some scans done and follow up with an orthopedician.
Take care!
Humans were not designed for running on hard surfaces. In time it can become a repetitive motion injury. Before modern man covered the earth with asphalt and concrete, every step we took was different from the last one. Think about that.
As runner, I hope you are aware of good supporting shoes and what your specific feet need. There are only three running shoe manufactures in the US that make shoes for supenators, and pronators. As we age not all of us retain the 'neutral' feet we once had. If you dont know what type yo are, I would suggest going to a real 'runners' shoe store. Many have a person very knowledgeable on staff the can watch your walking gate.
A real foot doctor or orthopedic understands correct/incorrect walking gate as well. If this continues there are also orthodics that can be molded for your feet and will lesson the stress on you ankles and calf muscles. There are several types of orthodics - the ones with a hard plastic bottom are to hard for running. Custom high density (stiff) molded foam is best for running.