Seems to b a secondary caries...although clinical evaluation is must for confirm diagnosis...
If ur tooth cavity is restored(filled) that doesnt mean that the rest part of ur tooth can not get decayed... If food remains there lodged for long period it will cause cavity. ..
Next Steps
visit dentist for needfull
Health Tips
for good oral hygiene brush atleast twice i. e. before going to bed n after breakfast... reduce in between snacks specially sticky n sweet ones... rinse after every meal..