So a few days ago I had allowed my boyfriend to suck on my nipple. He sucked for about 30 seconds then gave it a rest for a minute and then again. He also sucked the top part of my boob. It was not enough to give me a hickey, or to cause any visual bruising. However, it's been four days since the incident, and my boob has kind of felt a little tender, and the more sensitive toward the nipple area. Can something have happened when he sucked my nipple? Should I be concerned?