Sore nipples or breast

Hi. Can someone explain me if its normal to have a sore nipples? What does it mean if you had that? Its my first time to experience it. I had sex 4 or 5 days after my period last week of march..he did not used condom. He used the withdrawal method. I'm due to have my period next week based on Glow calendar..My sore nipples started last Monday..what does this mean?thanks for your replies..