It is hard to see exactly from that picture, but irritation from paper tape is superficial and looks like small bumps and redness on the skin. The area in the picture looks mucoid and necrotic. This may be a suture line infection or a result from decreased blood supply to the belly button. I use micropore paper tape on all incision lines after surgery and continue using the paper tape for six weeks. This has been shown to be as effective as scar gels and creams, and also helps with quicker fading of the scar color.
For now, stop taping, wash the area well with warm water and antibiotic soap. Then dry with a blow drier and call your plastic surgeon for an appointment tomorrow. Hope this helps.