u/Exotic_Passenger_150

I bit in to a hard honey roasted cashew the other day and it slightly hurt so I went to check in the mirror. I noticed thr tooth (upper pre-molar) is a light grey colour in a small patch. It wasn't there a few months back when I was inspecting my mouth. I can't get in to my dentist until next week and I have been stressing it is something serious. I grind my teeth a lot from stress and my bite is off. Any suggestions on what it could be and what will happen at my appointment to fix? Thanks in advance.