infected pus filled scratch

[rach27587]

Hey all
My first post here as I'm quite worried about my 7 week old.
At the side of his body near his bottom, the side wear the nappy covers....if that makes sense.
Well it started off he had a red spot type thing with a yellow head on it, later that day the yellow part spread into a kind of line so naturally I got worried and took him to the gp who said it seems to be a scratch that is infected, now I know it wasn't a scratch which I told him but the gp seemed satisfied that it was that as he said. He gave him some cream to use twice a day.
However overnight the pus filled part got longer.
Has anyone had this before on their little one?
I'm horrified at the thought of him having this as it is and now it's bigger/longer.
I'm a first time mother so I panic too much but just wondering if anyone can shed anymore light on the situation
I have added a picture to try help
Thanks in advance

[MrsLettuce]

I think, with such a young baby it's best to go back to the GP if you are in any doubt at all. Especially with it being Friday.

It's probably just fine, but still.

[MrsLettuce]

bump

[rach27587]

Thanks
I did take him back. They said not to worry still and use the cream and if it gets bigger they will give him oral medicine. However the raised part with the pus seems to have deflated slightly.
It just bugs me as I know it didn't start as a scratch so just hoping it goes away now.