Hello,
Looking at the picture,I can say that there are hard deposits on your teeth which is known as calculus. Because of it’s presence, your regular brushing cannot get all the way to your teeth for thorough cleaning. As a result of it there is now swelling in the gums and associated pain.
Next Steps
Next step : Please visit a dentist to get scaling (teeth cleaning and polishing) done. The sooner you visit, the faster healing can initiate.
Health Tips
Word of caution : Persistent long duration swelling can further get complicated and start affecting the bone in that area which holds the teeth. Because if which you might experience loosening of teeth.