I took my galgo, Cruz, in to see my vet a few months ago because he has one between his bottom eyelid and his eyeball. It's pinkish and a little bigger than a BB. Vet said it's a chalazion which is basically clogged meibomian gland (gland that produces the oily lubricant component of tears). Cruz will let me massage his and put a warm compress on it and it will drain and go away for a while, but it continues to plug back up periodically.
The "cure", according to my vet is surgical -- cutting a little slice out of the lid to remove it. I don't want to go that route at this point since it doesn't seem to be causing him any real discomfort or irritation to the eye and it's responding well to warmth and massage. I'd never heard of any of this before and when I first saw it was worried it was a tumor. I would let your vet look at it to rule out anything serious, but according to my vet this condition isn't uncommon, but some sometimes they can get big and very irritating to the eye.