My filly got in contact with a porky, her whole face was swollen, quilts way inside her mouth. I think she thought the porky was something to eat. The vet came and took them out, but the ones in her mouth were so imbedded, that he cut the tips off, to release the pressure, then they worked their way out, by themselves. In a few days, she was back to her own "naughty" girl ways.
Porcupine quills will work themselves out in the direction of their point. That means, if you miss it soon after the incident, it will find its way through the leg, nose, mouth, etc. One has to monitor for the exit by feeling for a tiny point across from where it made entry... (Out through the top of the nose in my uber curious porcupine chomping Dalmatian) ...then tweezers or needle nose pliers work well. Seemed a relief but required such sweet patience over a couple if months, to get them all (and that was after a vet, with Dal under anesthesia, removed as many as he could find...). What a day :(