You should see your dentist quickly. The longer you wait, the more compromised the tooth becomes. Decay or fracture into or affecting the pulp or nerve chamber of the tooth will exhibit pain, requiring a root canal and subsequently a crown. If the tooth is deemed non-restorable, it will be extracted and tooth replacement options will be discussed.
Hope this helps!
Once you are having pain in your teeth this is a possible indicator of the infection that is causing the decay having reached the nerve of the tooth. See you dentist ASAP before the pain gets worse, and/or the infection spreads. Good Luck!