i am on week 5 day 2 of c25k and i think i pulled a hamstring. the back of my knee hurts and there is a little swelling. i am basically look for advice about where i should go from here. anything would be greatly appreciated. thanks!
Hamstring issues can be especially annoying. They can take a long time to heal because people think they are good to go, get back to a normal workout routine, and then find out they're not.
You should ice, rest, massage, and take some ibuprofen if you can. Get back into your workouts at a reduced intesity, possibly start with just walking...swimming would also be good if you have access to a pool. I've use low intensity cycling as a way to keep getting some kind of cardio benefit when I've had hamstring issues in the past.
In any event, make sure you listen to the signals your body sends. If it doesn't feel right, back off. You could also consider a strengthening routine to help build up your leg muscles (not body builder build up) to help reduce the chances for future injuries.
It may not be the hamstring. You described it as back of the knee with some swelling, so it's probably not the hamstring itself. It could be the tendons that attach the hamstrings to the knee area. Treatment in that case is pretty much what has already been mentioned. But it also could also be Bakers Cyst (http://www.coolrunning.com/engine/2/2_5/194.shtml#bakers) A trip to the doctor may be worthwhile.