There’s a small lump on my dog’s belly; the seller said it’s from the umbilical cord not being cut properly. Is that right, and will it affect the dog’s health?

From the photo you uploaded, the dog has an umbilical hernia. This is usually caused by a developmental defect at the navel or improper cord trimming. The main symptom is one or more spherical bulges of varying size at the navel; these bulges are usually soft, painless, and not warm, and may contain ligament, omentum, or small intestine.

In puppies under 6 months old, an umbilical hernia may slowly heal on its own as it grows. But if the hernia is large, surgical treatment is recommended promptly.