Most everyday oral painkillers begin working within roughly half an hour to an hour, as the medicine is absorbed and reaches the bloodstream. The strongest effect typically comes a little later, and the relief then lasts for a set number of hours depending on the medicine.
If a painkiller is not controlling your pain, the answer is not to take more than the label allows, as this can be dangerous, particularly with paracetamol and anti-inflammatories. Taking more than recommended raises the risk of serious harm without necessarily improving relief.
If your pain is severe, not responding to the recommended dose, or lasting longer than expected, see a pharmacist or doctor. They can review the cause, suggest a different or combined approach, and make sure you are taking pain relief safely. Seek urgent care for sudden severe pain, chest pain, or pain with breathlessness.