What do i do about severe calf muscle pain?

i went to the gym and did a pretty hard leg workout. My calf muscles and the tendons behind my knee cap are so tight- i can't even straighten my legs. The tendons behind my knee cap feel like they could be inflamed. I'v been stretching but if i sit down for more than just 2 or 3 minuets they are so tight again and feel like im about to get bad Charley horses that it takes another 10 minuets to stretch out enough to simply stand on my feet awkwardly. than taking baby steps until i can some what limp and wobble. . . what do i do ?