You should never hide anything from your parents. It's called rebellion. The Bible says Honor thy Father and Mother. When your of age to be on your own then if you still feel you need one then your feel to do as you please.
Depends on how old you are. Many jurisdictions have laws that make it illegal for those under age 18 to get a tatoo w/out parental consent. If the tatoo provider ignores the law ...think : what other laws or health and safety processes are they ignoring? Wait until its legal and respect your parents.