Can't go to the vet untill friday, what should i do!!

[Ciddian]

Hiyas all,

I have a large male that is very friendly and active. A day ago i noticed that he had a limp but he was still walking on it, eating and drinking as if nothing had happened so i thought it was just a small sprain. I also felt along the leg for any sharp and pointy parts and didn't find any.
So i let it go.... Yesterday i came into check on my ratties and my big male was laying on one side snoozing. I peeked and his foot and freaked!....it's blown up like a ballon and is nearly four times the size!
Is this a result of a bad sprain,break or cancer??
I have moved him to a large flatt critter keeper so he doesn't hurt himself further.
He's still going about, filling his water dish with shavings and eating.... what should i do??
Has this happened to any of you before? What was the result?

I would really hate to loose him since i have had him from a pup. I used to use him at work as a way to get people who are terrifide of rats to love them. Some people still come and ask about "wilber"

Thanks heaps guys for any pointers you might have...