Is it what i think it is?

I hate telling this story but i have to know what actually happened; if it is serious or normal.... So when I was young, like about 4-7 yrs old, we were over at my parent's friend's house and we were playing hide and go seek with their older sons, ages 10-13 back then. I hid in the closet with one of the boys and he said to pull my pants down which I did... Then he pulled his down and said, I can still picture everything, he said, 'if u lick mine, I'll lick yours'.... I don't know why but I did and in return he did too.... I told my sister, my best friend (my cousin) and my parents.. Thing is I don't know if I should think of it as a sexual assault if we were both young... Just want your honest opinion please :) thanks :)