bk - If you're sore when you get up tomorrow, it probably means that you're "over-exercising" right now and suffering from self-induced exhaustion. -There is such a thing as "too much exercise".
One of the "dangers" of the treadmill is to push yourself and your limits a little faster than one probably should. If you've never run at that pace before, nor the distance, jump-starting your workout load in the midst of a stressful work-week isn't going to help matters.
Slow down. Take it easy.