You need to go see a doctor and have this looked at. It could be something serious besides cancer, like an infection in a duct. A doctor will be able to help you figure out what this is. If you're afraid to talk to your mom about making an appointment, then go to the school nurse, at least, and get her best advice. Please don't just wait for it to get better on its own, because it is obviously getting worse!
Let us know how it goes...
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