Why is my old username still showing on my branch?

Im not sure if I'm using the right terminology in my title...

So I made an account on GitHub a few months ago and am hosting myself a website with GitHub Pages.

I decided to change my username and got myself in a bit of a mess. I was commiting everything via MacOS Terminal as I didn't realise there was a GH desktop app at the time.

I've just realised in my 'branch' page it says:

oldusername and oldusername profile wording (*tick icon*)

Does anyone know how I can fix this? my new username shows everywhere else.

I suppose its not really affecting anything but I just find it annoying lol