In reply to SouthernSteve:
Too soon for strengthening if it's a calf strain.
RICE and stretching by using your shin muscles to pull your foot towards you until you feel a stretch , but short of pain, otherwise you risk more damage. Hold stretches for 30 secs and do 3 , several times a day. Don't use a strap to pull the stretch.
Eccentric exs are a bad idea, as this is probably not Achilles tendonosis from what you describe.
Best to see any physio and follow their rehab plan. Going back to activity too soon will lead to a longer lay off.
NSAIDS can be useful if you know you're safe to use them.