If she keeps hurting herself, you can make an e-collar out of a paper saucer. You tape it shut with for ex electrical tape so she cant remove it herself. Buy a whole pack of small saucers/plates o you can exchange daily after wound care. She should get some time without the collar on every day, but under strict supervision so you can stop her if she starts to self-mutilate again.
The wound should be cleaned. You can put neosporin or triple antibiotic cream (plain, no cortison or painkiller added) on it. Neosporin/triple antibiotic is OTC in the USA. If you are in Europe, you can use fucidine cream, which is OTC in several EU countries, but not all.
She is probably biting it due to some type discomfort, pain or itching. Rabbits that are really bored (f ex spend a lot of time sitting in a smallish cage, with no human present in the room) can also self-mutilate.
A pregnant or pseudo-pregnant (false pregnancy) doe can pick the hair from her dewlap to make a nest, but this as a rule wont cause sores because the hormones (same in pregnant and pseudo-pregnant does) make the hair loosen so it’s not hurtful to pull out.
It’d be really good if you could move the vet appt up or maybe ask the clinic to prescribe some meloxicam (antiinflammatory painkiller) that she can have until they have the opportunity to see her.
Is she eating and pooping like normal?