DOMS is a pain in the muscles felt anywhere from 8-24 hours after a workout or training, but seems to peak up to 72 hours (3 days) after workout. This sensation of muscular soreness is usually experienced after completing an activity you are not accustomed to (ie. a new activity or sport, or significantly increasing the intensity of your training). Interestingly eccentric work seems to accentuate DOMS. Eccentric muscle activity occurs when the muscle is lengthening as it contracts, as may be experienced during deceleration, changing direction and returning a weight to its starting position in an exercise.
The reasoning behind the soreness that is DOMS is that in your muscle fibers there are actually little micro tears as a result of your workout. Your body then triggers an inflammatory response to heal these micro tears, which leads to the feeling of aching and pain on muscle contraction. It is theorized currently that as these micro tears are repaired, the muscle fibre is made stronger and larger (called hypertrophy) and hence leads to an increase in muscular performance. This is not necessarily a bad thing!
However, sometimes it is tricky to differentiate between a severe case of DOMS and a minor muscle tear. If you recall feeling a specific grabbing sensation, or a sharp pain during exercise that is then followed by an ache, this may actually be a minor muscle tear (ie. damage). In this case, you should treat it accordingly with RICE (Rest, Ice, Compression, Elevation) and consult your physiotherapist. On the other hand, if everything felt fine during exercise, and you pull up sore over the next 24 hours in the muscle, it is more likely to be a case of DOMS. You should then monitor the symptoms and if things don’t settle after 2-3 days, then perhaps a visit to your Physio may be worthwhile after all.