I think my hamster has a skin problem?

Last year i bought a Habitrail Hamster Pad cage. It's the big round one with all of the awesome futuristic looking stuff. Any there wasn't much ventilation and my hammy didn't seem happy so i took him out and when i moved him into his more open bar Critter trail cage i noticed he had developed a large round circle like sore on his belly and i thought it was an infection from when he was in the other cage that my mom failed to clean while i was away. so i put some antibiotic ointment on it and it eventually turned into a scab and fell off. NOW it has returned in scab form. i clean his cage regularly and feed and water him so there is no mistreatment going on. I also noticed smaller/medium sized scabs around his back, sides, around the ears, and a fairly large one on his forehead. also his cheek has become really big and its not food because it is hardened and has been there for awhile, it also has a sore on it. I would take him to the vet but i am a minor and my mother refuses to take him because "he is a just a stupid hamster and she doesn't want to hear it". I feel terrible and i can't keep putting ointment on scabs that aren't going away. im completely lost at what to do and for now i am just taking as best care of him as possible and hoping he is in no pain.