Any Ideas What This Is??

[Kellys Heroes]

Guess the injury!?
We noticed this on our GSD this afternoon - its on her right rear leg, just below her hock.
Its almost like a little lump, but it lifts up and is attached at one end. Below it is like a clean hole (not bloody or weepy) and all around it, is furless! We first thought "tick!!!" but the lump is almost white and there is clear skin growth at the top of the lump - is it possibly still a tick?
We then thought maybe a little fat cyst - she's very 'lumpy' in her old age anyway, that she's maybe caught and its come away? Just odd that its so clean. We put some cream on her and it obviously hurts, bless her.
She did go over on her hindquarters this afternoon (chasing the baby starlings... at her age, I ask you!! ) but this was on plastic grass so I cant see anything having cut her then?
Any ideas welcome!!
K x
(P.S Please TFC don't move this....its not a thread purely for pics!!!)

ETA I did try to resize....seems I got the hang in one picture!!!!!!

 

[MiCsarah]

Sorry to say ths but there is an old terrier at my old yard who has a cancerous cyst on his leg that looks abit like that but slightly bigger. It started off quite small but is now as big as a thumb nail type size

 

[Kellys Heroes]

Sorry to say ths but there is an old terrier at my old yard who has a cancerous cyst on his leg that looks abit like that but slightly bigger. It started off quite small but is now as big as a thumb nail type size

Don't worry, thanks we will find out tomorrow we have booked her in at the vets - better to be safe than sorry!!
K x