Abscess?

Last November I had a root canal on one of my back molars. I know my dentist had a rough time with it, but he told me it was completely fine now. However, yesterday I woke up with mild swelling of my cheek. There's some swelling on the bottom of the gums close to this tooth (although it's not a bump per se) and it doesn't look like the abscess I had years and years ago nor is it painful. Even when I press pretty hard on it, there's no pain, just mild discomfort. The swelling increases after I eat, but goes down in between meals.

Here's my question:

Is it something really serious? I would normally just head to the dentist, but I'm currently in a foreign country (I came to Japan for studying) and my insurance doesn't cover dental health. I have a very, very limited amount of money for the next 5 months, and am hoping there is something I could do to prevent having to make an expensive trip to a dentist that I can't explain to.