What Causes Stabbing Pain At The Back Of The Thighs?

hi im a 48 year old man, and last week was playing cricket..i sprinted after the ball and felt a stabbing pain in the back of my thigh (hamstring ?).........carried on playing pain eased...next day had trouble bending my knee and walking upstairs.....been in pain all week with it, can walk but hurts back of my thigh, especially bending my knee...pain starting to ease, but still some discomfort..think ive strained or pulled the muscle...when im sitting down no discomfort..ive rested my leg all week, and kept it elevated.....been off work all week as my job involves a lot of stepping up and down off a train...how much longer will it take to ease completely?..is there any thing else i can do to speed up recovery.. thank you dave