If you did a workout yesterday and are extremely sore today—You overdid it. DOMS(Delayed onset muscle Soreness) -the normal stiffness within muscle fibres after workouts—Should start around 36-48hrs post workout. Doms can kick in earlier, but it shouldn't cause you to be extremely sore as you mentioned….
Were you doing a whole bunch of new exercises?
Runemist is on the right track—-gentle stretching and active rest(cardio, mimicking the exercises without any resistance or weight, and gentle stretching) will help flush out the lactic acid.
Just take it easy~~
Did you complete a good full stretch post workout? This is an extremely important part and should never be skipped. As I tell my clients—Warm up and cool down and not optional—they are MANDATORY. No room for debate….lol