Should I have told my grandma about this?

I was over my grandma's house last year and while practicing riding on a big bicycle it started to get a little bumpy and I looked over at my granddad and noticed he was looking at me in a weird way like he was looking at me in a pervy manner.I was twelve at the time by the way, when I got off the bike he asked me a question I thought was inappropriate ''is you're vagina okay?''.I thought it was a weird question and I think I might've answered ''okay'' but really I wasn't sure how I should've reacted should I have told my grandma about this?