This potentially has a life threatening consequence if left alone. The only choice is to see a dentist or oral surgeon, as it likely needs to be extracted. This first visit needs to be a conscious one, but the treatment visit can be a sedated one. If you can tolerate not being sedated, your first visit can be a treatment visit.
You may be developing an infection. I would highly recommend seeing your dentist sooner than later, since cases like this are always easier to manage at the beginning.
I would strongly recommend you see a dentist soon. It is likely the tooth has become abscessed and needs to be treated. If the tooth is this badly damaged it will probably be extracted. Don't wait any longer. It will only get worse. Your dentist will take good care of you. Good luck!