Going through a tough workout or an exercise activity that your body is not used to and you will most likely find soreness 48 hours later.
Your muscles will experience tiny micro tears to the muscle fibers which is a part of building muscle. D.O.M.S (delayed onset muscle soreness).
To best remedy your sore body, increase your protein intake (for muscle repair) stay hydrated, and lightly exercise the next day to increase the oxygen and blood flow to the area. Rest and quality rack time will speed up the repair process as well.