For the last few days I've been having trouble with one of my top back molars. First, the roof of my mouth adjacent to the tooth swelled up a little bit and was tender like it had been irritated. Now the swelling is gone, but it is still a bit tender when I push on it. I am also getting dull little aches now and then on the other side of my tooth (outer side).

Could this be a cavity? I already have a cleaning appointment but it's not until the end of the month.