Welcome to BYC.
Sorry to hear about your duck.
It sounds like we're dealing with an injury here, and I say because of the suddenness of the limping, it would also make sense that when she pulled the nail off she sprained/injured her leg at the same time.
By chance could you upload a video of her trying to walk to a video platform like Youtube or Vimeo, and copy/paste the link here?
Does the leg feel warmer than the other? What breed is she?
What I would suggest would depend on the severity of the limp. If she's not able to put any weight on the leg at all, and it's swollen. Starting her on an NSAID like Meloxicam, ketoprofen, or Carprofen might be suggested, these are RX only, so a prescription will be needed from a vet, or of course, you have already on hand from a past visit. In addition to this, keeping her in a soft padded area that reduces her risk of reinjury would also be good as well as daily soaks in magnesium sulfate (Epsom salt).
If she is able to put some weight on the leg, and it's only slightly swollen. Some "bed rest", daily soaks in Epsom water, and administration of B vitamins, or aspirin would probably best as far as the lines of treatment.