Sounds like she has an abscess she is trying to drain. Cats open up sores and lick it to try to heal it. She needs to see a vet asap but until she does a warm, wet washcloth applied to her leg may help ease the pain and drain some poison out. Please make sure she gets to the vet for antibiotics. She could die if the poison is not removed.
Assumptions do nothing but make an ass out of u and me.
We can stick our heads in the sand for only so long before it starts choking us. Face it folks. The pet population is bad ALL OVER THE WORLD!