Little Baby Squirrel/Super Cute/Super Healthy/BIG BUMP :(

[millyquu]

I recently came across a little baby Grey Squirrel fallen from its nest in my backyard it was infested with flees so I cleaned it fed it some home made Pedialyte. I tried multiple times to get it back together with its mother but with no luck. so now I'm stuck taking care of this Poor thing, which I don't mind ( its not the first time I've had squirrels in my care ) the little thing still has its eyes closed and is still way to young to let free. I've been giving it Esbalic Puppy Milk replacer and it is super healthy. although, there is one thing that I had just noticed since I left it to sleep as much as possible for 3 - 5 hours with minute 3 - 5 minute feeding periods. But I had just noticed it has a Big Bubble/Blister on its chest which I don't believe was there when I found it. ( its been 3 Days ). I do recall a lot of flees being in the area that has been inflamed but I had cleaned them and used a light mix of soap and water until it was completely free of a flee infestation. what is shocking is how fast it became inflamed because I would of noticed this lump upon finding the squirrel, especially since I did a very through inspection of any leftover flees. ( it is very big in comparison to the baby squirrel ) if anyone is familiar with this problem please let me know what I can do to familiarize my self with a remedy I don't want to do anything until I know what would be the proper procedure.

DESCRIPTON

-The bump is very soft to the touch almost like a blister.
-It doesn't seem to irritate or hurt the little baby upon caressing it.
-It appeared overnight