Stone in my salad

I bought a chicken avo salad at one of your branches in marshalltown which took 24minutes to make and i was that patient, when i got to work and was eating, i chewed a stone which irritated my teeth which i had to leave work for because i wasnt feeling so good anymore...this ruined my teeth, im too scared to eat now and they are super sensitive now. please clean up food, this is not healthy and im sure it is *******