My 6 Year Old Has Redness Around And Inside His

My 6 year old has redness around and inside his belly button. It has been 3 days he also has been suffering with headache and on and off fever. Took him to pediatrician who felt he may have a virus and irritation at belly button. Prescribed hydrocortisone pint but today looks like maybe white substance deep inside bettybutton. Any idea what this could be?