If it's the front milk tooth you can get it extracted since the permanent front teeth erupt between the age of 6 to 9. If it's the posterior teeth you'll need an xray to confirm if it can be saved or extracted as they erupt between 10 to 12 yrs.

Extraction should be considered as a last resort. With advances, milk teeth can now be saved by performing painless root canal therapy. Depending on the extent of decay extraction or root canal is advised As for the permanent teeth, an Xray of the region will give a clear picture about the presence or absence of the successor. Rarely are the permanent teeth missing, in case of which retaining the milk tooth for as long as possible seems beneficial. A visit to a Pediatric dentist will help you clear your doubts better