Dog constantly licking something on his paw, what could this be?

1 year old male Australian Cattle Dog. He is constantly licking his paw and it seems to be tender to the touch as he pulls away when I touch it. I will be getting him to the vet next week for a health check anyway so hopefully our vet can have a look. In the meantime is there any way to tell what this could be? I'm so worried.

https://imgur.com/a/OmY8Mfb