Why didnt you start off on something easier if you knew you were out of shape, there is no point in working out 'hardcore' if your not ready for that kind of stress on your body. The only thing you did is hurt yourself, so now you will most likely take off a lot of time to recover from your 'hardcore' workout and not be exercising, while you could have done 3 mid-intensity workouts in the same amount of time and had much better results.