silver nitrate newborn belly button

Hi all!

So my 2 week olds umbilical cord fell off 7 days old on the dot. all looked well and he has a little hernia there but I guess his belly button has not closed all the way (?) and they treated it with silver nitrate according to his father (he went to the appointment while I stayed back with our toddler). is it normal to see yellowish discharge for a lack of a better word inside his belly button since the treatment? i know on the inside it looks grayish/blackish on the perimeter from the testament but on the actual inside of his belly button is where the yellowish discharge is. it looks like it could be sticky. have you ever dealt with this? do I clean the inside or let it do it’s thing? what are the care instructions for this? thank you!