Hello,
Regular maintenance of oral hygiene is important & in your case you might suffering from deep caries with pulp involvement i. e the most sensitive layer of the tooth causing the trouble.
Next Steps
visit dentist for further clinical examination to avoid further damage & get the necessary treatment done.
Health Tips
Please follow proper brushing technique with fluoride containing toothpaste & ultrasoft toothbrush twice daily on a regular basis.
Also, DON'T delay the visit to dentist & avoid self medication.
Thanks!