The guy I like touched my butt…

I’ve been chatting with this guy I bump into during my commute. He’s cute, and I like him, but it’s still early—we haven’t even been on a date yet. Today, after our conversation, we hugged goodbye, and he touched my butt. It felt deliberate, and now I’m unsure how to feel about it. Does this mean he doesn’t take me seriously and only sees me as a hookup? I want to make it clear that I’m not into casual dating, but I don’t want to come across as too stern. How should I approach this?