What I thought was a small tumor...now has a scab?

[hsm]

So, for the last couple of months I was POSITIVE that Blue was growing a small tumor behind his front leg. I've been saving up money, selling things, desperate to try to get him into the vet to get a surgery consult (which would have been 100% possible at the end of August, when I start school again and get financial aid). I was hoping to get him in sooner, rather than later, and have been drafting a post for the garage sale section for a while to try and sell some hammocks (been spending a lot of time trying to figure out the cheapest shipping).

However, I was checking all my boys over last night, and I felt his lump to see if it was any bigger. I ran my finger over it, and it felt rough. So I flipped him over, to his indignation at such treatment (much flailing of his tail and squirming) and parted his fur to see a scab. Now I'm confused... It might be an abcess, but if it is, it's closed over? I don't know. I'm going to take a picture of it later, to better show you all what it is.
The scab is entirely closed, and dry. No oozing, and it doesn't LOOK infected. But now I'm frightened, because he's had this lump for a couple of months, and now it has a scab on it...and I heard abcesses should be left open, but it's been inside forever, and now has a sealed scab?
Or maybe it is a tumor, but he's been scratching/biting at it?
anic:

 

[victoria]

Do a warm compress... if it's an abscess the scab will likely come off and reveal the yuckiness underneath. (Save the money you did save in case something else comes up if it is an abscess.)

 

[jorats]

Yep, I agree with Victoria.

 

[hsm]

Is a warm compress just a warm, damp washrag? If it is an abscess, is there a particular thread that goes through how to care for one?
I'm probably going to take him to the vet anyhow, because if it is an abscess it's probably pretty deep - the lump has been there for a couple months.

 

[Roo]

I didn't read through all of this, but it's generally a good site I believe. Perhaps give it a look through

http://ratguide.com/health/integumentar ... bscess.php

 

[xKrAzEdShOoTeRx]

interesting, i learn a lot from this site

 

[hsm]

Alright. I read through it. I've got myself a kit set up, to try to figure out whether the compress will reveal an abscess or a conundrum... Got a washrag, a bottle of saline solution (it's too hot right now, I'm waiting for it to cool a bit), a large towel for my lap, and cotton swabs.
I'll post before/after pictures. I got a better look at the scab today than I did last night, and it looks kind of yucky. My initial thoughts about it not looking infected are now different.

I just don't understand... If this is an abscess, why did it take so long to come to the surface?

Edit: Ok. Well, I tried. He disagreed... squirming, flailing, SCREAMING. I think I'm going to need my mom's help with this... But I also think it hurts him now (which it didn't before).... I also couldn't get a picture of it.