Often wounds of this sort will heal on their own (it's called secondary intention healing) although it may take longer for them to do so than if they were sutured soon after the injury happened. They also often look worse than they really are.
The biggest concern is infection, of course, although antibiotics aren't typically available over the counter and require a prescription. If you might have access to any human drugs, though, please let me know and I can provide dosage amounts if they're antibiotics which might be useful in this situation.
But, for now, the following is what I'd suggest that you do:
1. Cleaning with sterile saline is better than hydrogen peroxide (which can retard healing) but it doesn't have anti-bacterial properties. Instead, I'd flush the wound with dilute over the counter Betadine or Iodine (to the color of weak tea) twice a day.
2. After it has dried, then I'd apply over the counter antibacterial ointment such as we'd use on ourselves.
3. I don't typically recommend bandaging these types of wounds unless the patient is constantly licking at it. And, even then, I usually suggest a cone for a few days to prevent access.
4. A perfect product for this wound would be Vetericyn Spray which can help to increase healing time. This spray is often available at local pet/grain stores or can be purchased online.
5. I doubt if Effy required any anti-inflammatory drugs or ones for pain if she's moving around just fine and not lame; however, Aspirin can be given as long as she's not vomiting nor currently taking any nsaid medication. The dose for a dog this size would be one, 325 mg (full strength) tablet twice a day, with food to avoid stomach upset.
If the wound starts to ooze or look pusy or inflamed, then it might be wise to have her seen sooner, if at all possible. Hopefully, though, the above at home treatment should prevent this from happening.
I hope this helps. Deb