My rubbish calf

Went for Week 4 Day 2 of Couch to 10k and within 10 minutes of setting off I could feel my calf muscle tensing up, despite the 5 minute warm up I religiously do. I pushed on and completed the time I had to do but really progressed to much more than a fast walk because it was so painful. Hopefully can repeat the same days exercise again tomorrow and it will feel better.