Whilst I can't condone your course of action, I would be a hypocrite to say that I haven't at least considered it myself, and I understand that your motivation was concern for your pet. Although the surgery appears to be a success you run a serious risk of infection and you need to be extremely careful to keep the wound clean. Do you have anything antibacterial which is safe for axolotls? I do believe the leg had to come off which I why I previously recommended you consult a vet - I'll recommend it again here - you may have only delayed the onset of septicemia/blood poisoning if you haven't removed all the infected flesh close to the shoulder. Good luck - hope he recovers OK...