Am I just being triggered or is it sexual assault?

My uncle lives with us. He is my favorite uncle. Tonight. So we were eating dinner and I was helping with my mom with something. And my uncle was cleaning after him. Well when he walked he passed my butt and he like hit it. I don't know if he was trying to be funny or not. This is the first time he did something. And I am scared because my brother-in-law did sexual abuse to me. So am I just being triggered or what??? Advice please!!?!

EDIT: I did speak up to him. After he did that he looked at me and I looked at him and I said eww stop. And then we went out separate ways. But the reason I spoke up this time because I didn't do that last time with my brother-in-law.