Scrape as much of the glue off of the sofa as you can without spreading it further into the fabric. If you have a cloth-upholstered sofa, you can use a straight-edge blade to remove most of the glue. But if you have a leather sofa, use a letter opener or a spatula to avoid scratching the leather.
Dip a rag into acetone, then dab the acetone onto any glue that still remains or is still hardened on the sofa. Try to avoid getting any acetone on the sofa fabric.
Let the acetone rest on the glue until it begins to soften. Scrape the rest of the glue away with the blade, spatula or letter opener.
Mix 1/2 cup distilled white vinegar with 1/2 cup warm water in a spray bottle.
Spray the area where any glue or glue stains remains until the area is lightly moistened.
Blot the rest of the glue or glue stain away with a clean sponge.
Rinse the area with a sponge moistened with clean, cool water and then dry with a soft, clean cloth.