What to do

My boyfriend and I were not using a condom the other day. And he texted me saying like hey I got like a drop of com in you, I'm so sorry what are we going to do, but I'm not on birth control. My next period should be in about 12 days. Should I just use a Plan B to be safe, because we are still in HS? Or what, I have been freaking out send a he told me this. HELP!