I would go to see your primary care doctor
about this issue, especially if the redness and pain is worsening. They can take a look at your navel and help you decide what treatments might be needed.
Just like anywhere on the body, the navel can be a place where skin infections develop. In fact, given the fact that the navel is a humid and not always completely clean environment, there is a predisposition to infections there. Although most of the time these infections are mild and respond to good skin hygiene and topical antibacterial ointments, occasionally they are more severe and might require additional medical treatment, such as lancing to drain the pus or oral antibiotics to bring the infection under control. Your doctor can take a look and decide whether this is what needs to happen.
Rarely, there can be anatomic abnormalities inside the navel that persistent from life in the womb, where small tracts that previously connected internal organs to the outside do not close entirely. These can be the sites of recurrent infections later in life. Your doctor can also help decide whether or not this might be going on in your case.
Make an appointment as soon as you can!