Should I still take Plan B?

Kinda long sorry :/ 
Okay so I just moved to PA and had my bf drop off my prescription for my birth control at Walgreens to have it filled, I needed the new one to take the first pill of the pack that day. Well I didn't know pharmacies closed so early here as compared to NY, so I ended up missing that first pill and my boyfriend ended up ejaculating inside me that night before I could tell him not to. I talked to the pharmacist the next day asking if I should folllow the instructions for a missed "active" pill (take the one I forgot immediately, then take the one for that day at my normal time) and then also take Plan B? Or just do the BC? He said just take the birth control pills as directed on a missed pill and I should be safe from being pregnant. I'm not sure though, I was hoping to get some opinions on here. Should I take Plan B as well, just to be safe? Thanks in advance!!