Tetanus shot? TERRIFIED. Help?

So my mom decided to inform me that I need a tetanus shot before I leave for a mission trip...in one week....when she told me, I blacked out. I DON'T DO SHOTS. I can't even remember the last time I had a shot and I'm seventeen! I am SO scared. I'm considering backing out of the trip because I DO NOT want to get that shot. Especially since I've heard it's the most painful shot. I'm a hypochondriac and have an EXTREMELY low tolerance for pain. The slightest pinch hurts me. I'm absolutely terrified. I don't know what to do because I know she's going to make me get it and I honestly cannot do shots. I'm terrified of the reactions and side affects and so much more. I don't know what to do... How bad is the shot? And the side affects. NOTHING mean please. I have a HUGE fear of needles, pain, doctors, alllll that. :(