Sudden pain on my left teeth, what should i do?

Slight or severe?: It may be nothing, but then again, it may be a fracture, a cavity, or an abscess. Can't tell without an exam, so that's why you will need to be seen locally by a dentist in your town.

First time?: If you've had this only once, it may be nothing. But if you have it frequently / daily then it could be a more involved dental problem. In either case, you need to see your dentist for a thorough examination and radiographs (x-rays) to determine the exact cause of your severe pain and the appropriate treatment.

Most, but not all, dental pain is caused by infection. The appropriate response to pain is evaluation to determine the appropriate cause of treatment for the cause of the pain. Please call a Dentist.