Can I bring a claim against a restaurant that denied tree nuts being in their products but pecans were in it causing an allergic reaction and ER visit

I bought my boyfriend a cookie from a bakery in our town for his birthday. He is deathly allergic to tree nuts so I am always cautious when buying things from small businesses. I found a "peanut butter chocolate" cookie and asked the girl assisting me three seperate times if the cookie contained any nuts (most people do not know the difference between a peanut and a tree nut allergy). I even went as far as to state "he will die if he eats a cookie with tree nuts in them". Even with a nervous laugh and explaining verbally that cross-contamination could occur she assured me that this specific cookie did not have nuts. Well, my boyfriend ate about half the cookie before beginning to feel his allergy symptoms: congestion and throat closing. Of course, the cookie had pecans in it. So, he had to be taken to the ER - thankfully we live right across the street from a hospital to receive treatment just before entering anaphylaxis shock. He is thankfully okay , but what can I do?