Have you tried putting her on crate rest for 24-48 hours to see if the limp will resolve on its own? Allowing her to continue behaving normally is preventing it from healing and may be making it worse.
Crate rest means in the crate for the duration, and all potty breaks are on leash. Out to toilet, then back inside…no walks, no play.
Take him to the vet. Whatever this is (and my unexperienced layperson’s opinion says it COULD be a luxating patella), it’s not something you can fix at home. It may require surgery.