There are several conditions that can cause the symptoms you have described. Any such occurrence with regard
to the umbilicus requires urgent medical attention given the potential to develop serious infections
originating from a defect of the umbilical wall. This can be cellulitis or necrotizing fascitis and both have
potentially serious and life-threatening effects.
Disorders of the umbilicus involve fistulae, urachal sinus, urachal cyst, umbilical granuloma, umbilical
infections, umbilical hernia, etc.
You will need to seek medical attention at the earliest to identify the exact cause and extent of the problem
and to have it receive adequate treatment at the earliest.
It is definitely not a good idea to wait till the 26th. Call your doctor and fix an appointment to meet within
a day or go to the ER.
Do keep us posted on your doubts and progress.