Veterinary questions? Ask a Vet for Answers ASAP
Hi, Welcome to Just Answer. I'm Chris, a small animal Vet based in the UK. I am reviewing your question and will get back to you as soon as possible
Sorry to hear this. With the degree of swelling her I would suspect either a fracture or dislocation of the leg, or a massive infection if a traumatic injury has occurred here such as a bite.
I'm afraid without pain relief or antibiotics this little ones chances of survival are likely very poor. If the leg is broken then it will not heal. The kindest thing would probably be to take it to a local vets for them to put him to sleep. They will do this for you free of charge.
I'm sorry fo that was not the answer you were wanting, but it is likely the best thing for this rabbits welfare.
Please let me know if you need any further help or advice.