Temporary crown, sudden black tooth. Should I be worried?

Hi, I had a temporary crown put on after a root canal about 6 years ago, I understand ideally I would’ve had a permanent crown put in place by now but it just hasn’t been financially possible. I have had my annual cleanings between then and everything seems fine. However this week and next I am on vacation for the holidays and I have noticed a large black spot has suddenly developed. Should I be worried? I’m freaking out.