What is causing my toothache and how to stop it?

You do not say what type of pain you are having. Is it constant throbbing or pain when eating or with cold or hot things? Or is it due to eating sweet things? If it is a constant throbbing, it is more than likely due to your wisdom tooth coming in. But only a dentist and an x-ray can determine what the actual problem is. Rinsing with warm salt water will not help with the pain, but may help with any swelling that you may have in the are. Try taking Advil or Ibuprofen for the pain. These are anit-inflammatories and will help with the pain.