19 years old, and had tetanus shot 8 years ago. just got inch long scratch from rusty nail that barely penetrated skin still had blood. what to do?

Not at risk: Cleanse the area well. A superficial scratch is not a risk factor for tetanus. Tetanus comes from dirt embedded deep into tissue.

Booster: This is a good time for a "booster" injection of tetanus toxoid. Repeat about every 10 years.

Rusty nail: Wash and clean ound, apply an antibiotic ointment and it wouldn't hurt to get a booster tetanus shot even though your tetanus shot is good for 10 years