Dull pain after a workout results from microscopic tears in muscle fibers caused by intense activity they’re not used to performing. Which when this happens it usually leads to- Delayed Onset Muscle Soreness, or "DOMS." This occurs when muscle pain doesn’t completely set in until 24 to 48 hours after exercise. When the pain limits strength or range of motion, it’s best to take a hint from our bodies and give them a day or two off. Working out damaged muscles often opens the door for further injury and setbacks in a routine.