Wtf is this in my sons belly button?

[TitsalinaBumSquash]

It seems to be flesh, attached to him and can extend like a worm and can also be pushed back in almost like an umbilical cord not healed on a baby but he's 13 and it's very sore.

Skin tag? Might be a touch sore/infected??

I’d wash with cooled boiled salty water and let the air at it. Then off to the GP tomorrow x

Do let us know what the doctor says. Very strange!