Cut yams can be stored in the refrigirator for upto 5 days. 
Yam contains calcium oxalate crystals which can cause irritation in the mouth and throat if eaten raw or not fully cooked. Boil the yam well and roast with masala and spices. Can also be baked and sauteed. 

Yams are a good source of vitamin C. They also provide a good amount of fiber, potassium, manganese, and metabolic B vitamins. The content of vitamin B6 is good for shrinking the effects of homocysteine, which can do real damage to cell walls and ultimately lead to heart attacks and/or stroke. 
The crunchy edible root is chiefly composed of complex carbohydrates and soluble dietary fiber.