I'm concerned because it is very common for unspayed females to develope mammary cancer in dogs, so it IS important that you get her seen. Fortunately, in dogs, it is very easy to treat most of the time if it is caught early. Speaking from personal experience, my dog had surgery for mammary cancer at age 5 and lived until she was 18 and hers was pretty advanced, so treatment DOES work.
You need to keep the area clean so she doesn't get it infected if she is constantly licking it with peroxide and you can put neosporin on the area to help keep bacteria out. If she absolutely refuses to leave the area alone, you'll need to go to a petstore and get an Elizabethean Collar (or fashion one yourself out of plastic or cardboard to keep her from getting to the area and irritating it more. These look like cones that are put on her head.
I would definitely get her in as soon as possible. If she keeps on messing with it, you'll have a pretty severe infection on your hands.
Please let me know what the vet finds!