Baby mouse with one puffy cheek

Question
I got a baby mouse a few weeks and I left town, I came home to him having a puffy cheek, he's in a cage with a mouse a little older then him but he's extremely nice, I doubt it's a bite from him, what could it be?

Answer
When you say 'cheek' do you mean the side of his mouth or the part where his whiskers grow? The latter is most likely a nip from the other mouse or he may have injured himself in the cage. It should heal up by itself. If it's the side of his mouth check to see if theres a problem inside. He may have an abscess or food trapped in his mouth.

If you are still concerned take him to the vet. I hope he gets better soon. Please feel free to ask any more questions.