What can be done for facial paralysis and numbness after root canal!?

This is unusal. Not only unusual, but concerning. Be evaluated by an endodontist or oral surgeon. Ask your dentist to refer you to a provider he trusts. The sooner the better.
Hard to say. This question is best answered by a specialist who can see you, take a medical history, and discuss exactly what went on before, during, and after your treatment for this tooth. Too many variables to be answered intelligently over the internet.