I know you feel bad, but remember, it was an accident, and she'll get better.
Take some saline solution (like the kind you put on contact lenses) or some hydrogen peroxide and rinse her paw well. Pat it dry with a towel, and then coat it with antibiotic ointment like neosporin. Keep an eye on it over the next few days and make sure it doesn't look like it's getting infected. If it becomes infected, it will get very swollen, and an abcess might form. If it does get infected, take her to a vet for antibiotics.
Hopefully she'll do fine with the home treatment and be better in a few days.
