I did that too to poor Roxy 'p-private' area...
I felt so bad. She went a whole day b/c I couldn't get her to the Vet. She was 'scooting' around the WHOLE house 24/7. On the title, the hardwood floor, the rugs. And she was SO MAD too - she would make these grunting noises.
Oh, I felt horrible! I took her to the Vet and he rubbed her down with something, gave her a shot and gave me some antihistamines for her, OH and a BILL for $70
...LESSON LEARNED HERE