Sex after IUD

I got Kyleena yesterday afternoon, and the doc said "nothing in your vagina for 7 days". well that blows, because my boyfriend is coming over this friday. does anyone know if this rule is just protocol so i don't get pregnant or can there actually be complications if we have sex? i'm starting my period this week as well. i was just gonna have him use a condom, but he said to listen to the doctor. i thought i'd get feedback from you experienced ladies, though. (also, can he cum inside me??)