There's no cure for being zombified so here's two recommended actions depending on how you'll react to realizing that you are doomed to a hated-by-all existence of being a member of the undead.
1.) Oh... oh god... *breaks down weeeping* (Don't wanna kill anyone?)
In that case, write your will, turn on a body cremation machine (what ever, the machine that people use to burn bodies), and crawl into it. This way, you'll burn your body before it can claw its way out of a coffin and start the world's worst flesh festival. It'll be painful, though, so make sure you're either doped up on something and you're in Lucy in the sky of diamonds or reeeeeeeeeeeeeeeeeeealy drunk.
2.) "I'll take the French man rib covered in Italian blood with a side of a American fingers." (silver lining in the cloud)
If you want to make the most of this and bring on the terror of the zombie race in full swing, just walk in front of a speeding bus. Bam: Instant dead. Because it'll be a public place, filled with people, people will be curious, get close to see what happened... and you can just jump up and start snacking like it's the end of the world, because it is and you brought it. Screw everything that happens after that, just start getting the taste difference between type O and type A blood.
Good luck, hope this helps.