Hi.. There must be something stuck in between the teeth and the gums that is the reason why you have pain in that region.
Next Steps
Visit a periodontist and get deep cleaning if possible curettage done in that area, by doing so you will be free of pain and can avoid infection. After cleaning mouthwash for few days is advisable.
Health Tips
Don't delay because the food which got stuck in that region might turn into pus and infection.