Mild muscle soreness after exercise (delayed onset muscle soreness) is normal and usually settles within 2-3 days with rest, hydration, and light movement. It isn't a sign of injury.
What to watch for: pain that appears suddenly during activity accompanied by a 'pop' sound, significant swelling within a few hours, a joint that feels unstable, or pain that gets worse instead of better after a few days of rest.
Other signs that need prompt examination: pain accompanied by numbness or tingling that spreads, being unable to bear any weight on the area at all, or fever accompanying muscle pain (which can signal something other than a sports injury).
The principle is simple: rest and ice are enough for ordinary mild soreness, but once any of the signs above appear, a direct exam by a sports medicine specialist is safer than waiting and hoping it resolves on its own.
