Could be a cut, a bite, something stuck in
there, a growth of some type, etc. You can try soaking in
an Epsom salts soak a couple if times a day, add it to some warm water in something she can stand in. Keep it dry and try to keep her from licking it. Easier said then done but you could try some Vet wrap. Why do you have to wait two weeks to go to the Vet? If it looks worse, more swollen, *****, bleeding, etc, you should get it checked.