Plan B ???

My boyfriend and I were having unprotected sex this morning. I was on top and he said he was going to come so i jumped off and he finished on himself. He started to look worried so I asked what was wrong. He said he held it back but felt something while I was still on top. We are now worried about it. I am supposed to start my period in 9 days. Should I take plan b or am I okay since i have already ovulated ? Also, I am really scared for the symptoms of plan b !! Is the nausea bad?