My kitten is in so much pain! What should i do?

I have a 9 month old kitten that lost one of her back feet before she was born when the umbilical cord got wrapped around her ankle. She has been living a happy full life since i rescued her and hasnt had any real problems with her 'nub' other than the occasional scratch and a mild infection once. I dont have money to take her to a vet so I've been providing the best care i can. The last few days it has been causing her enormous pain though. She howls and screams and falls over from it... its horrible to watch! Shes delibrately destroying things and attacking people and other pets out of pain and I need to do something! What can i do for my little angel??