In the past I have tried many different methods to protect the area. The most obvious, a bandage, was too clumsy and thick, interfering with my manipulation of the knitting needles. I tried a leather quilters' thimble and it was also too cumbersome. I then tried using fingercots but they dulled the sensation of my fingertip too much making it feel like I was knitting with gloves on.
I have finally found a near perfect solution.

A humble piece of masking tape. It works great! It protects my finger just enough to prevent the shock of a needle ramming into an open wound, but isn't bulky and also leaves enough sensation in the fingertip so that I can still feel what I am doing.
As you can see in the picture, eventually even the masking tape wears through but at $1 per roll I can afford a new inch or so of tape whenever that happens.