Tetanus symptoms usually show up 4 to 21 days after you've been infected with the bacteria that cause the infection.Most commonly, symptoms start after about 10 days, but it can be as little as one day or as long as several months.hey then spread to other muscles, such as: 1  chewing muscles – making it very hard to open the mouth (sometimes called lockjaw). 2  throat muscles – making it difficult to swallow. 3  facial muscles – making it look like someone is grinning. 4  neck muscles – making the head tilt.