What do I do with a sick bird I found?

Ok so one day I was in patio and I hear chirping , I look down and see a bird (a budgie) so I bring it in and put in a secure place. I looked at it more closely and saw it had ball thing under it's stomach. Im pretty sure it's a tumor. Now I don't know what to do . Should take it the pound would they take care of it or what? I can't take it to a vet cuz it to much money. What should i do?