The tip won't grow back. I'd say keep it and the cage clean, apply neosporin once or twice a day.

The tip probably fell off because it was already dead due the cut off blood supply- the fact that there was blood indicates that the rest has a fair chance I'd say to stay on. Just keep an eye on it for any signs of infection but it is such a small wound it should heal up well.

Don't feel so bad, it isn't your fault the snake had stuck shed!