It sounds like it could be a chalazion. I had never heard of this until I took my galgo, Cruz, in to have his eye checked for a small growth in his lower eyelid. Anyway, it's basically caused by a blocked oil gland. The term is sometimes used interchangably with stye but my vet says there's a difference, but some websites say they're the same thing.
This is from a dog health website online:
"Chalazion (ka-lay-zee-on). Retention or blockage of oily secretions from the Meibomian gland extravasates into surrounding eyelid tissues and induce a granulomatous inflammatory response. Clinically a chalazion appears as a firm, nodular, yellow-gray mass through the palpebral conjunctival surface (Figure 5) and is painless. Chalazia occur more frequently in dogs than in cats and most commonly occur secondary to a Meibomian gland adenoma which block secretion of the Meibomian gland. Treatment requires surgical curettage through the conjunctiva.2 The skin is not incised. Aftercare consists of topical antibiotic-steroid solution for 5-7 days."
Cruz has not had any surgery or treatment for his. I massage it and sometimes use a warm compress on it when it gets larger. He's very good about letting me do this. Right now it's all but gone, but it does tend to get blocked and will enlarge again and I repeat the process.
Let us know what your vet says.