Numbness, pain, infection after root canal?

I had a root canal on lower left, # 20, 5 days ago. Although it was not abscessed, I was having a lot of pain & trouble with this tooth over the past year. I was told that the tooth was dying, (a crown was already in place after having old amalgam filling removed), and that a root canal would most likely take care of the problem.
I have had other root canals that were no problem.
The day after this root canal, the left side of my lip became numb. The next day my lower jaw became numb and I began to experience a severe amount of pain. By the third day, I was experiencing swelling and the pain became more severe.
Haven't been seen by endodontist again, but contacted by phone over the weekend, and was told an infection developed, was given antibiotic, (10 day course), and pain meds three days ago. I believe the pain and swelling has lessened but the numbness remains. I am planning to call endodontist tomorrow but wondered if anyone had any advice or maybe give suggestions about what kind of questions I should be asking my endodontist.
I am really getting concerned that this is something bad and troublesome.  
Thank you in advance.
Meli
PS Also my tongue feels like its chapped (?) or burning. I have the same sensation on the outside of my lip too. I guess it is due to numbness for so long??