Did i cross a line?

My boyfriend (24M) and I (23F) have been seeing each other a few months and have always been comfortable talking about intimacy. asking for what we want to try in bed things like that. Basically the other day he started pulling on his balls during sex. I asked him if that’s something he wanted me to do and he got a bit weird about it. he didn’t even acknowledge it was something he did. I think it may be something he’s embarrassed about and i’m afraid pointing it out i’ve made him feel like he can’t be as vulnerable with me or something. We’ve been intimate since but it feels like somethings off. how do you fix when you accidentally cross a boundary like speaking about an unspoken fetish? and was it wrong to ask about?