It could be so many different things, Gail, if she doesn't seem in pain,
I'd not give her aspirin until the issue is known as it thins the blood and
can cause stomach irritation & perhaps bleeding. I'd keep her crated &
quiet until you get her in, do you have a regular Vet? It could be a soft
tissue injury, a sprain or muscle pull or other, more serious issues.
Please keep us updated, I'll add her to prayers list.