You should keep him out. I had some problems with my milk snake getting nippy about a week after I got her. I just held her for a few minutes after she bit me, after I learned how she prefered to be picked up (not near her head at all), she began to make it less of a challenge for me to get her out. Now I can lift up her hide and pull her out and set her on my hand before she even starts moving around.

Hope I helped