I think each one of us has a fear similiar to yours. If you think that's a bad fear, it isn't really if you put it into perspective - knifes are dangerous but only used in the incorrect manner. People get scared of all sorts of strange things like balloons, chewing and heinz baked beans - I kid you not. Yes, knifes can have destructive power, but you must wave this fear or else it will begin to affect you.
I have a strong aversion and fear of injections. But this spans from when I was younger (my father is diabetic and used to inject himself infront of me). As a consequence I haven't had my TB vaccination, meningitis C, dipetheria injections. But I'm starting to grow out of it, and I may schedule to have my meningitis C after I had a scare last year at Uni. So don't worry, people are going through the same thing!