I need advice.

Okay ladies I don't know if over exaggerating about this so please help me out..... My boyfriend and I have been together for 2 years and we always watch tv well when their is girls who flash their boobs on tv his penis gets hard mostly every time and I notice and we will fight about it last night he finally admitted that it's true but he says he don't know why it happens he doesn't think about them like that but he sees a pair of Tities and he gets hard. Should I worry about this? Or just let it go???