Thanks everyone, you are a very helpful bunch. I did stop the peroxide
- wouldnt have thought of doing so unless I was able to get to Vet
quickly (not possible) so your suggestions were helpful. Strangely, it
does appear better today. We are taking him to the vet on Thurs - she
is the best vet and we wish to wait for her to return.

If the wound subsides, we will use the picture that I posted to show
her the progression, or vice-versa.

I just cant imagine what this whole thing is from - disease or wound.
Still puzzled about that.

Can you stop by the vet's office and get an e-collar to prevent her
from scratching it anymore?

Please, if the wound worsens or your cat has other symptoms
(lethargic, won't eat, fever), call your vet and request an earlier
appointment.