FIL groped me!

We went to visit my husbands parents who we only see a few times a year because they are not nice people and my husband only sees them as little as possible to 'keep the peace'.

Anyway my FIL hugged me and ran his hand down my back and onto my ass. Thought maybe it was an accident but he kind of squeezed. I ignored it. Later when we left he hugged me and his hand brushed my boob.

I told my husband on the way home but he thinks it was an accident but it didn't feel like accidents! I got that horrible feeling in my gut.

What do I do?