I had a root canal done awhile ago, the filling came out shortly after and now it's hurting what's going on?

It's possible that your tooth has become reinfected or possibly fractured. I would recommend seeing your dentist right away for an evaluation. A retreat may be necessary followed by a crown to seal and protect your tooth. Good luck and I hope this helps. Follow me if you have more questions.

when you have a root canal the permanent filling and coronal seal is as important as the Rootcanal itself. Research shows if the rootcanaled tooth is exposed to the oral environment, for more than 30 days the Rootcanal system is reinfected and the tooth will need to be retetreated prior to putting a new crown on.  

After a root canal, a permanent restoration is absolutely required to avoid fractures and another infection from developing.  I recommend you visit your dentist immediately and have the area evaluated.