For 1.5 days, my belly button has been very sore (not sharp pain). the pain has not spread, gotten worse, or better. what might this be?

Belly Button Pain: It could be a superficial infection to something more involved, depending on how deep the pain is. Bladder or bowel (colon and appendix) are possibilities of deeper issues. These are usually accompanied by other symptoms. Skin infections, like yeast or cellulitis, a common superficial infections. I would suggest making an appointment with your doctor for an exam to determine the cause.