Hi. I'm Dr. Gotthelf. I have been a skin and ear vet for 35 years and I would like to use my experience to help you with your pet's medical problem.
It could definitely be an insect bite that she is irritating. There are other things that can cause this type of lesion. Dogs that "root" to get under a fence or a door can get these. Bacterial infections can also cause swelling. If it has turned pink on the black part of the skin of the nose, it could be an autoimmune disease called discoid lupus. Your vet will need to check it since it has lasted a week. The treatment will depend on the diagnosis and it can range from an antibiotic to high dose steroids.