Yes indeed, its very important to tell other people the effect on the person that has gotten bullied.
1. the physical of the person will change gradually when they got bullied
2. there is a chance that the person will have some kind of trauma
3. the personality of the person that always bullying other people will become very bad (impolite,rude,etc)
and there is still many more example why we should tell other people on issue of bullying.