I'll bet that shook you up bit.
Well the most important thing is that you had that muzzle pointed in a known safe direction and that nobody was hurt.
Remember that exact instant when the firearm boomed unexpectedly?
I'm sure that you froze with a total startle response.
The reason I say "remember that" is because that is exactly what will happen to you if you are ever suddenly and unexpectedly jumped or attacked.
It's an interesting human reaction.
Concerning your Negligent Discharge. Be thankful that nobody was injured or worse...and then get over it and move onward & forward.
Bad Stuff Happens Sometimes...and then what we do as thinking and responsible human beings is to learn something valuable from it and then get on with life a little bit wiser.