This is due to deposits, please visit a dentist , go for scaling ( hardly it takes 30 min). This is painless procedure. Once it is done, it takes 2 to 1 week to be cured completely. You might be feeling sensitivity for 1 week.
Health Tips
During this 1 week,
1.continue brushing twice daily,
2.use mouthwash for 1 week
3. use both sides for chewing.
4. do gum massaging in those areas
5. Use antibiotics as per the advice of the dentist.
Nothing to worry, if scaling is completed.
Hope this helps sir.