There are basically two types of pain you might experience as a result of exercise. one is casued by stress on the muscles and connective tissues resulting in pain that appears after exercise and typically dissipates within about 48 hours. Then there’s the more acute pain that comes as a result of an injury.
The trouble is we may not always be able to tell the difference.
Some research reveals that taking ibuprofen may result in cancelling out the muscle growth that occurs after exercise. There’s also evidence that our bodies release their own anti-inflammatory substances and this can be suppressed if we take other anti-inflammatories.
In short – injuries need to be treated but not all pain is the result an injury. Taking painkillers and anti-inflamatories may be unhelpful unless you are actually injured.
Source: Business Insider – Why you shouldn’t take painkillers after working out