idk if i have been sexual assaulted in my past

so i was 13 at the time and it was summer. all of my cousins and their friends were here for the summer at their lake house. i was hanging with the two boys that are my age by the campfire and my older cousin who was in his 20s was there too. i went to go charge my phone in the house and when i was walking back out to the fire, my older cousin grabbed me and started touching me and grabbing my butt. i didn’t know what to do at the time and still havent told anyone about it bc i didn’t think it was a big deal, which now i do. what would you consider this to be?