You said that you don't allow the mouse to run loose in the enclosure to avoid bites, and yet your snake got a nip on the nose anyway.

I feed live in enclosures every single week. I've never had a problem with my snakes getting injured from a rodent being allowed to wander in the enclosure before being constricted by the snake.

You may not have had any problems hand feeding to date, but one day, you may be in for a big surprise when your snake misses the rodent and constricts your hand instead.