Puffy Spots Under Eyes

I know this isn't a dire emergency since my chin is still very active, eating well and pooping up a storm but I'm worried.

He sees the vet on Friday because he has developed puffy circles under both eyes that are a bit larger than a nickle. His eyes are clear and bright with no drainage, crustiness, or wateriness.The bumps are pretty noticeable and I'm worried what it could be.

I don't have a pic to show. I'm wondering if anyone has dealt with this before or has any ideas?

Thanks