Calves swelling is not a common condition. There are a few possible diagnoses to consider, and unfortunately some of these are serious. I would recommend seeing your primary care provider to rule out serious conditions.
The most concerning cause of calf swelling would be deep vein thromboses or DVTs. While not likely to be sudden and bilateral--this is potentially life threatening. Essentially a DVT is a blood clot that spontaneously forms in the venous system (the vessels that bring blood from the muscles back to the heart). These clots can form from multiple conditions--the two most common are a thrombophilia (or blood clotting disorder) or an undiagnosed cancer. The real concern is if the clots in the legs break off and go to the lungs--which causes a pulmonary embolus and may even cause death. The calf is swollen and tender. To rule this out alone I would see your primary doctor
Other causes are more rare. A Baker's cyst is a common condition in which part of the joint behind the knee forms a growth. This is normally not concerning, but if it ruptures it can cause a swollen and tender calf. If this is the case, pain medicine can be given until it heals.
Other causes could be from muscle inflammation--a myositis. There are many types of myositis which can be from many causes. Simple muscle inflammation from overuse is another cause--in fact the most likely.
Fluid overload--from heart problem or kidney problem or liver problems can also cause swollen calves. Again these are more likely in older patients--it is possible and must be ruled out.
I would see your doctor to rule out a few concerning causes of swollen calf.