A tire leak could result from loose nails, screws or other pointed objects that may puncture and penetrate the tread. This will result in a flat tire and will need immediate attention. Running the car with a flat tire could permanently damage the rubber, negating the possibility of repair. When faced with a flat tire, stop the car in a safe area and replace the tire immediately. Leaving a flat tire on a car may damage the steel threads embedded inside the tire, leading to tire deformation.

Take note that a tire leak will need to be repaired immediately to prevent any further damage. If the puncture is deep and has completely penetrated the tire then you will have to bring it to a certified shop to have the tire dismounted from the wheel, and patch the tire from the inside by a professional. Remember that patching a tire is the best way to repair a leak. The DIY enthusiast will make do with a tire repair kit, which is a lifesaver in most emergency situations.
A tire plug kit does not require you to dismount the tire from the wheel, but you will still have to jack the car and remove the wheel to accurately check where the leak is coming from.

Also note that damage to a tire's sidewall is impossible to repair; only damage to the tread area of a tire can be repaired.

If you have damage to the side wall, it can not be repaired. Green area Yes. Red area NO

Never drive your vehicle on a flat or punctured tire! Doing so is dangerous and likely to damage your wheels.

How to Repair a Tire Leak

• Materials Needed
   Tire plug kit
   Jack
   Tire wrench
   Cotton rag
   Pliers
• Remove the Wheel
  Loosen the tire nuts with a tire wrench and jack up the car. Remove the wheel from the hub.
• Inspect the Wheel
  It is easy to find a leak in the tire, as a nail or screw will have a visible head protruding. Pump the tire with air and inspect for leaks. If a nail is evident, carefully pull out the nail or screw using pliers. Remember to mark the hole with chalk or any other tire marker. For hard to find or small leaks, mix soap with a little water and work up to a lather. Use a small sponge to apply the soapy mixture over the surface of the tire. When bubbles form on a particular area, you have successfully located the leak.
• Use the Tire Plug Kit
  The tire plug kit will contain a rasp tool to clean and roughen the hole. Insert the rasp tool in the hole and quickly it pull out. Take the plug provided in the kit and fill with cement. Use the insertion tool to fully insert the plug into the hole. There should be at least an inch of protruding plug after it is inserted into the hole.
• Let Dry
  The cement and plug is designed to dry instantly, but let it dry for at least a minute before cutting the excess plug from the tire surface. Use scissors or a cutter to snip off the protruding plug.
• Measure the Air
  Pump the tire with air and check for the correct pressure. Apply some soapy mixture onto the plugged hole to double check the seal.
• Replace the Tire
  Put the tire back on the wheel hub and tighten the nuts accordingly.
  Remember that a tire plug is deemed a temporary solution to cure a tire leak. It would be best to have the tire dismounted and checked by a tire dealer.