When you have a toothache you should see a dentist as soon as possible.
Tips
usage
牙痛 functions as both a noun ('a toothache') and a stative verb ('to have a toothache'). 我牙痛 = 'My tooth hurts' / 'I have a toothache.' No 是 needed.
culture
There's a famous Chinese saying: 牙痛不是病，痛起来要人命 yátòng bùshì bìng, tòng qǐlái yào rénmìng — 'Toothache isn't a disease, but when it hurts it can kill you.'
