Is it against to my sons human rights for indivualisation and the law to stop my son expressing himself by having an eye piercing (which he is willing to cover with a plaster and it is not interfering with his work or distruping his class in any manor)?

I don't think individuality is technically a human right in the sense that you're describing it. Most schools have dress codes and standards which they expect their students to adhere to. These rules are in the US primarily set by the school district and the superintendents office. A list of the rules is generally given to each student at the start of each term and many schools require both parent and student to sign a waiver saying that they have read the rules and will obey them while the student is enrolled at said school.
While, I'm willing to agree that an eyebrow piercing is not disruptive in the general sense, your school district seems to think otherwise. And unfortunately, unless the rule is changed there's not much you can do about it. You could attempt to have the rule changed by appealing to the school district and by attending school board meetings.
Rules of this type are not intended to discourage individuality, they're put in place to maintain a professional standard.