How do you handle fetish admission from boyfriend?

I just found out my boyfriend has a secret fetish and it’s new. He said he recently started loving it and I am not sure how I feel about it. It’s not familiar territory and something I am grossed out by. I was honest and told him I needed some time to process this information. I told him some things I am not willing to try. So has anyone else experienced this? How do you deal with it? Is it a deal breaker? How do you get to common ground? Thank you!!