First of all check out your statute of limitation in your state.
I live in OHio, ours is one year, ours is one of the lowest from any state I think.
You can ask the dentist if he will re do it for free, if he is an excellent dentist he probably will if someone told you it was not seated properly and this is why it happened.
You can also notify your county dental society to see if he will pay to have it redone if
you do not want to go back to him, but first check your statute of limitations, this is the most important thing of all.
You should definitely bring it up to your dentist first to discuss your situation and see if you can come to a resolution first. If you aren't satisfied, you can contact your local dental society to see if they have a peer review board that can settle the dispute.
http://www.ada.org/prof/prac/tools/peer_review_overview.pdf
Same thing happened to me and I had to pay for a new crown because the dentist that performed the procedure had an office in another location. UGH! It always smelled funny when I flossed and I had mentioned it during my 6-month cleaning but no one seemed to tell me why until a few weeks ago when I was getting a root canal on another tooth! You should definitely contact the dentist who did it because he/she should've seen in the x-ray after it was placed that it was poorly seated. Have them redo it for free- you shouldn't have to pay for their mistake like I did!
I am not a dentist, but i a crown that did not seal properly and i ended up having the tooth pulled!! It started smelling bad because there was a sepage of food underneath the crown. GROSS. I had to pay for everything, it was only 4 years old. If it is not sealed properly make sure to get replaced asap befor ethis happens to you.