If it is an initial caries ( its called incipient caries) you can prevent further spread by the usage of flouridated tooth paste, mouth wash rinse and flossing. ( Dental floss is available in market). It is applicable only for initial caries, if it has gone beyond your enamel layer you must seek treatment soon. Otherwise it is definitely going to spread further.
Next Steps
consult your dentist soon.
Health Tips
Regards
Oral care dental clinic, kannur, kerala