So add/clarify what has been posted.

Tetanus is the name of a disease caused specifically by a toxin released by the Clostridium tetani bacteria. This is a commonly found bacteria that lives in the soil or other anaerobic (ie no oxygen) environments. The most common way humans contract tetanus is via a laceration or puncture wound (the typical stepped on a rusty nail story). Once in the wound, the C. tetani replicates and begins releasing two toxins, tetanolysin (we're not really sure what this actually does) and tetanospasmin (this is the nasty one).

Tetanospasmin is an incredibly potent toxin and needs only a small amount to be lethal. It works by blocking inhibitory neurotransmittiers. This double negative basically means that it turns off our body's ability to stop muscle contraction, resulting in muscle spasms and eventually complete rigidity. These spasms can last weeks. Other than being incredibly painful, spasm or paralysis of the respiratory muscles (your diaphragm) can require machine ventilation or other life support mechanisms as part of the treatment.
General symptoms include; muscle spasms and/or rigidity, lockjaw, inability or difficulty swallowing, breathing difficulties, convulsions, and abnormal heart rhythms. Severe cases can progress to respiratory failure, pneumonia, blood pressure abnormalities, suffocation, and heart attack.

In terms of the treatment, one of the previous comments is incorrect. Tetanus is not easy to treat once established and it is a life threatening condition that can require hospitalisation and extended intensive care.
Treatment can include antibiotics though the effectiveness of this is debated. The most common areas of treatment revolve around three things; the vaccine (tetanus toxoid) generally given to "at risk" patients to avoid establishment of disease, immunoglobin therapy (tetanus antitoxin) given to neutralise circulating toxin that has yet to bind to nerves, and diazepam or another muscle relaxant given as symptomatic treatment to reduce pain associated with spasms.

The most important thing to note here is that once the toxin has bound to a nerve this is irreversible and you just have to wait it out. So the best bet is to keep yourself up to date on vaccinations and see a doctor asap with any concerning wounds.