Okay... I am not a doctor, a nurse, an x-ray tech, an orderly, an acupuncturist, a holistic healer, nor am in anyway qualified to give a medical opinion. So here goes...
Heras won the Vuelta with stitches in his knee. This is a 55 mile ride, not a three week stage race. Are the stitches on a part of the calf that moves while pedaling? If there is no movement, I would say you're good to go. If it feels like the stitches and the area held together by the stitches could tear, don't ride.
And ask your doctor.