Pain in the upper right jaw that started with gum swelling and now hurts mainly while chewing is most likely due to a tooth-related problem such as a gum infection around the last tooth, food impaction, early tooth decay, or irritation from a partially erupted wisdom tooth; even if the swelling has reduced, the underlying issue may still be present. At this stage, you should maintain good oral hygiene by gently brushing, rinsing with warm salt water 2-3 times daily, and avoiding chewing on that side, while using a simple pain reliever. However, the most important step is to visit a dentist for examination, and if required, an X-ray to identify the exact cause. Treatment may involve cleaning the area, removing trapped food, treating decay, or managing the wisdom tooth if it is the source. Seek prompt care if pain worsens, swelling returns, or you develop a fever or difficulty opening your mouth.