My hamster Teddy (Syrian Hamster) is ill!

Question
Dear Mrs./Ms. Gutteridge,
                        My hamster Teddy is un-well! The side of his cheekish are is swelling. It's red, shiny, and big. Poor thing I don't know what has happened to him. What do you think could have caused this? And my mother will not let me take him to the vet since we just took him about a few months ago regarding a flu. SO simply my questions are; What has happened to him and what could have caused it? And since I can't go to the vet what can I do to help him at home? Oh and if it touches something will it hurt him, and I'm scared that it may be a rash and I dont want to get infected, though it may not be, well thanks you for your time and consideration for answering this question.
                                      Sincerely,
                                  A Hammy owner in need

Answer
Hello,

Is it just the one cheek or both? Is it leaking blood or pus or anything? Does it have an opening or is it something on the inside of his body that has caused it?
Is he eating and drinking?

Let me know the answers to these and i will see if i can help.
Thanks,
Charlie.