Delayed onset muscle soreness or DOMS is a type of muscle pain and soreness that sets in a few hours after an exercise. It is not uncommon to find people complaining of aching muscles one or two days after exerting themselves in the gym or after a dramatic increase in the duration or intensity of their exercise. DOMS is also common in people who just started out on a new exercise programme.
The exact cause of DOMS is not known. However, it has been thought to be a result of micro-tearing of the muscle fibers. This microscopic tearing of the muscle fibers is also associated with swelling in the muscle, which may contribute to soreness. The swelling can build up for days after a workout, and this explains why the muscle soreness may be worse two to three days after a workout. The extent of tearing, and hence the amount of soreness, will depend on the type of exercise we do and how long we do the exercise.
The soreness should go away in 3-7 days without special treatment. To speed up healing and reduce DOMS, you can try going for a massage or use the R.I.C.E.R method. Also, there are research showing that warm-up performed immediately before an exercise session can produce slight reduction in DOMS.
However, if your pain persists for longer than 7 days or increase despite the above measures, consult your physician!