I'm 34yo, 28 weeks pregnant and woke up with a "golfball" knot on th back side of my right calf. It lasted a few minutes of varying intensities (8-10 on pain scale). I was sleeping on my right side. I've tried stretching (toes up, heel down), walking around the house, laying on left side and warm bath.... The pain has remained a 5. What gives?
With the pain being very acute, topical ice would likely be more effective than heat. You should otherwise continue stretching it, and staying off your feet for the day, and it should resolve within hours.