How responsible is my contractor for work his workers did in my house 2 years ago?

We had our house renovated 2 years ago and last month the ceiling in our kitchen started to leak. Thinking that it was a problem with the upstairs plumbing we called in a plumber. The plumber found that the worker who renovated our bathroom, hammered nails into our water pipe while installing the floor molding. It cost us $3000 to have the work repaired as he also did not seal the toilet. There is water damage and mold that has to be corrected along with the walls that had to be cut and the ceiling has at least a 6' x 6' hole in it which still needs to be repaired plus the tile floors in two bathrooms need to be removed and replaced. The water pipe runs between and adjoining wall between two bathrooms. We contacted the contractor who came over and said he was not responsible because his warranty is only good for 1 year. He did say he would fix the ceiling but we are not going to use him as I don't want his people back in my house. I requested his liability insurance which he has not supplied me with which leads me to believe he doesn't have any. Do you have any advice as to where I can turn to make this contractor responsible for the work his workers did in my house. After all, this is not just normal wear and tear but just bad workmanship.

Thank you for your help.
K.T.