Lump on hamsters throat.

[fawnthehamster]

So, my hamster Henry has a lump on the top of his throat that started about a week or so ago, but he was still acting fine and running around and whatnot. This past week hes starting to struggle when hes walking and is dragging his back legs a little. I was just wondering if anyone knew possibly what this could be? A few people have said it could be a abscess or a tumour but I dont know the difference and I wanted to know that if he was in pain what should I do?

He has a vet appt this afternoon at 3pm so until then I've just got to wait around.