My temporary crown cracked, what should I do?

I had a root canal 2 weeks ago. Last week I my dentist put the post and temp crown on. I go next Friday for the permanent crown. I woke up to find my temp crown is cracked. Should I call my dentist Monday when they open and tell them? What can I do to prevent more damage or it coming off at all over the weekend? I think I may be grinding my teeth at night, what can I do to protect my tooth at night? It is my number 4 tooth.