If you can get someone to help you, use a tongue depressor to open his mouth.
While keeping it open, GENTLY press on the spectacle of the eye. Gently steady pressure is the key. If it's a blocked duct, you should see some of the fluid leak out of his mouth and the swelling should go down.
Don't be alarmed if there is a dent in the outside of the spectacle.
While his mouth is open, look at the roof and see if you can see any swelling or redness. If so, he really should be treated with antibiotic drops 2x a day for 10 days or so.
If gentle pressure applied to the spectacle does not yield any positive results, or if for any reason you are squeamish - see if a local rehab center could take him in.