I know we have some medical professionals on this site….

I’m wondering if anyone has some idea what we are looking at or dealing with here (pic included)
It’s my 4 year old granddaughter and she just suddenly ‘grew’ this blister-type thing on her hand.
She says it didn’t itch but it was hurting

It’s been present for a few weeks now, and it has shrunk in size. Also, it’s not as ‘full’ or plump/juicy as it was at first.

They are waiting for her appointment with a doc but I’m wondering if anyone has some suggestions as to what we are dealing with…whether it might be contagious….or even some generic, cross the board type of topical ointment we could use on it in the meantime?