Thanks for posting your query.
Pain may be due to the decayed molar in which the decay has spread into periapical region causing pain on gums,tongue etc.
I would suggest you to visit a dentist
Thro' clinical as well as radiological evaluation,tooth has to be restored or root canal
Take complete course of antibiotics too.
If the decay is very severe,tooth has to be extracted.
Take vitamin becosules,c,iron supplements
Use fluoridated toothpaste and soft-bristled toothbrush to clean your teeth.
mouthrinse to gargle.