Sometimes the humane society can give you some directions on how to care for your animal. Sometimes you can simply ask a vet a question. Do NOT drop your animal off at the Humane Society. Try not to get any more animals if you can't afford to care for them though. Pets are kinda like children. You shouldnt have them if you can't take care of them.
I would call a Vet and consult. Remember Fish stores have Antbotoics at a lower price. They are the same thing but in a lower dosage and half the price. It sounds like it needs to be cleaned and wrapped. Use a bath towel and gently wrap the cat so it will not struggle and hurt it or you. Then use mild soap and peroxide. You might have to shave some fur around the paw. Then wrap with some 4 by 4 cling pads from the first aid kit. Then wrap with medical tape. You will not be liked by Fur ball but it needs to be cleaned. Just calm and pat and show some love. Or take the easy route and take it to the Vet.