How do i help a feral cat with injured leg?

my feral cat got either frost bit or he has a object stuck in his paw or a broken leg,i can't always pet him,but how can i help him? he doe's know i have his preg. fem. mate inside..he tries to look inside my porch..but won't come in..what can i do..or who can i call to help him that won't put him down?