Swelling or puss-filled bulb

My cat has some sort of injury on his front leg. It is a round spot that seems like the fur was scratched off, maybe from bark or a cat fight, but there is no scratch that i could see penetrating the skin. It also is round and bulbish, and i dont know if it is swelling or just a puss filled area, or something else. It does not seem to hurt him when he walks, or restrict him, and didnt mind me wiping it or applying pressure to it. Is this anything i should be concerned about?

It's hard to know, without seeing it.  If there are any signs of infection, a visit to the vet may be called for.
 

Is it a mass? It could be just a simple fat lump that has gotten irritated and opened up. Your cat coild have had it for a while without you noticing then something could have irritated it which would result in the loss of hair and oozing. I would keep an eye on it. But you stated before that it doesnt seem to bother your cat which makes me think it is just a lipoma (fat bump). Usually lipomas have no feeling to them.if it starts to show signs of infection or it starts to hurt then I would for sure bring the cat in.

If you could get a picture up I would loce to see it!

He popped it, and yes, it was filled with puss. But now he has a large sore that we need to get bandaged, so we are taking him to the vet tomorrow. Thanks for all your help!

Likely treatment is antibiotics and bathing it a couple of times a day with warm water (possibly slightly salty water) to keep it open.  Abcesses have to heal from the bottom, if you let them close over then the infection restarts.  They usually heal very quickly, and hope all is well at the vets.