This could be becoz of strain of achilis tendon ..You try icepack for every 4 - 6hrs and try stretching gently your calf muscle and then Luke warm water fermentation
Next Steps
if pain doesn't subside still after 5 days of therapy..then u need to visit a physio for further evaluation and care...
Health Tips
before and after exercise you should mandat warm and cool down so you avoid such pains in future.