Help!!!

Okay so little story. My bf and i were in sexy time but he’s on this medicine so he couldnt get hard all the way. He put a condom on anyway even though he was like 3/4 of the way hard and then like 1 min into sex i asked if the condom was still on and he checked and it came off when he pulled out. I’m not sure if it came off inside me or what but he hadn’t cum yet so I’m only scared of precum. So should i buy plan B or be scared?