Thanks to immunization, the tetanus illness is very seldom in Switzerland (1-4 cases per year) and even if you're unlucky, lethality is considerably lower than in developing countries (< 25% compared to 40-50%).
That said, it's important to have proper immunization.
Another place to go if you're in a hurry (open around the clock):
Airport Medical Center (AMC), Zurich Airport, Phone 043 816 60 00
The AMC medical practice is somewhat difficult to find though. It's located in the same building as Parking A, between Terminal 1 and 2.
http://www.klinik-gut.ch/english/s_airport_e.htm
The Permanence at the train main station is generally nice for minor problems but queuing is indeed very common there.
So in case of a real emergency (the mere risk of a tetanus infection probably doesn't qualify) I'd recommend to dial the appropriate number:
http://www.linker.ch/eigenlink/sos_notfallnummern.htm
and/or visiting the A & E of the nearest hospital. Please note that more and more patients visit A & E departments of hospitals for obvious bagatelles, potentially preventing other, needier patients from being treated in a timely manner.