You walked from Viana to Oia what is roughly 50 kms and gathered 1 stamp a day at least .
For applying a Compostela you need to gather 2 stamps a day for the last 100 kms to Santiago.
As Jungleboy and Ivan Prada already mentioned , these 100 kms either start in Vigo what supposedly was on your Coastal route or from O Porriño on the Central route.
The stamps on the trail from Vigo to Pontevedra you’ll miss so the person at the desk of the Pilgrims Office will notice that by checking the stamps in your Credential.
But you can apply for a touristical certificate at the desk , a souvenir of your caminho.
This costs you a few euros .
And of course keep on collecting stamps. Your credential anyhow is a nice document to keep.
And the best with your ankle
Bom caminho