Oooh, poor Russ! Gosh Breyer, I am the same as you...I know it is always a hard decision to decide whether to put your baby through the stress of a vet visit and of course, it is too bad humans don't speak rat, otherwise we could ask our rats if something hurts them, eh? 
Maybe, if Russ does not seem to be limping or favoring his other front foot, and if he does not seem to be licking or pawing at it and he seems as normal as always (i.e. playing, eating, grooming) then maybe it just looks nasty but it doesn't bother him at all? Wow, wish I could give you better advice, but I know how hard it is to do the vet visit and stress out the kids! Hmmmm...
Maybe, if Russ does not seem to be limping or favoring his other front foot, and if he does not seem to be licking or pawing at it and he seems as normal as always (i.e. playing, eating, grooming) then maybe it just looks nasty but it doesn't bother him at all? Wow, wish I could give you better advice, but I know how hard it is to do the vet visit and stress out the kids! Hmmmm...
