Didn't your grandson have an eye infection? Looks like you've got it now. Conjunctivitis is extremely contagious. If the baby rubbed his eye and you touched his hands, you could get infected that way. If any of his blankets came in contact with his eyes, and you handled them, you could pick up the infection.
My pediatrician told me when my daughter had conjunctivitis to treat both eyes at the same time (only one eye was affected) and to sterilize her washcloth.