Do you guys see anything on my X-rays my dentist might've missed?

I went to the dentist November 25th, they took X-rays and said I had a small cavity on my 18th tooth and to just come in for a filling. But the problem is 5 days after that on November 30th the gumline and lymph node near my 19th tooth(specifically between it and my 20th tooth) started to hurt.

I don't understand why, because my dentist looked at the X-rays and didn't say anything. And it sucks because it was 5 days after my visit, and my next visit is in May. Is there actually something wrong with that tooth, or are my gums just irrationally in pain? Is it possible to schedule an emergency visit for it?