I understand your concern. Hepar sulphur 200 is a homeopathic medicine and it is not recommended to give such high-potency remedies to a 3-year-old child without proper medical supervision. There is no scientific evidence that it can cure dental cavities or reliably relieve severe tooth pain.
If your child is having significant pain, it usually means the cavity has progressed and needs dental treatment, not just medicine.
Next Steps
Take your child to a pediatric dentist as soon as possible
The dentist may suggest fluoride application, filling, or other treatment
Maintain good oral hygiene with supervised brushing using a smear of fluoride toothpaste
Avoid sugary foods and night-time feeding if still ongoing
Health Tips
Home remedies or homeopathic medicines cannot treat cavities
Delaying dental treatment can lead to infection, swelling, fever, or abscess
Early treatment helps save the tooth and reduces pain quickly