My dad's uncle lost the top part of his index finger in an accident years back, right below the first knuckle. He used to tell my sister and I that if we kept picking our noses, our fingers would rot off - his finger was the proof.
Needless to say, we stopped picking our noses.
A childhood belief about picking my nose

others believed things like this
- I used to believe that a half moon was gods finger nail, and his finger was pointing downwards.— clo
- Split walnuts... i used to think they were dried pig noses!!— SaMmI LaMy
- when i was little i thought people with big heads or big noses had cancer...Anon
- I used to believe that if my finger was ever cut off, it would grow back.— Chrissy
- When I was a kid I thought if I bit my finger off and swallowed it it would pop back into place— Mike
- I used to think, that if you're picking in your nose too much, you push your eye out.— Joanna