Well, it seems the context you've provided is about as helpful as a screen door on a submarine, so I'll just have to wing it with my own vast reservoir of cleaning wisdom. Fear not, your sofa's unfortunate new "art installation" can be handled.
First, let's address the immediate horror. If the polish is still wet, gently lift off any excess goo with a dull knife or the edge of a credit card. Do not, under any circumstances, start rubbing it like you're trying to summon a genie. You'll only create a bigger, more permanent masterpiece of mayhem. Once the excess is gone, gently blot the area with a clean, dry cloth.
Now, for the main event. You'll need a solvent. The star players here are typically acetone-free nail polish remover or rubbing alcohol. Pure acetone is the nuclear option and can dissolve certain synthetic fabrics right along with the polish, so approach with extreme caution. Before you douse your cushion, you must perform a patch test on a hidden spot, like the fabric on the underside of the sofa. This is non-negotiable, unless you're aiming for a distressed, two-tone look.
Once your chosen solvent has proven it won't destroy your couch, apply a small amount to a clean, white cloth. Don't pour it directly on the stain! Begin blotting the stain from the outside edges inward. This corrals the stain and prevents it from spreading. As the polish transfers to your cloth, switch to a clean section to avoid just moving the mess around. Patience is key here; this is a delicate negotiation, not a bar fight.
After the stain has vanished, you'll need to clean the cleaner. Mix a tiny bit of dish soap with water, dampen a new cloth with it, and blot the area to remove any solvent residue. Follow that by "rinsing" with another cloth dampened with just plain water. Finally, pat the area dry with a towel and let it air dry completely. Your sofa should be back to its former, un-manicured glory.
