Of course, there's more than just nursing. I know a couple of people who wanted the same as you and they're both on their way to becoming clinical psychologists. One of them, I know, is particularly interested in working with criminals.
You don't say how old you are, but you'd do well to have a chat with a careers advisers and look at your options. If you're still young, then that will be via your local Connexions branch or school careers officer. If you're older, an enquiry at the job centre will point you in the right direction.