Take it from me, a dog bite is bloody agony, your vet should be able to dispense a shot of finadyne for you to collect.
Please let her have some pain relief, there are no doubts she will be sore and the quicker she is pain free the quicker she can recuperate.
I was going to leave it at that but I can't, sorry.
A sheep is a prey animal by the time it is showing ANY symptoms of discomfort it is pain. Dog bites are ragged lacerations with deep puncture wounds, liable to become infected within hours.
If you had such a wound on yourself would you leave it and not make a fuss?
The fact she is baring weight on it is no indication that she is not in pain, more a marvel of a species who after being attacked by a pack of dogs will not be left behind the flock.
You have a duty of care under the animal welfare act, and I hope for your sheep's sake you get her some meds.
You won't even have to pay for them, the dog's owner will pay it.