I would take him to the vets if he was mine, but if it's not worrying him I'd wait until Monday rather than pay the extra for a weekend appointment.
If the tooth is wobbly it possiblly needs to come out, even if it looks OK. Perhaps his gums are receding and that's causing the problem? My almost 12 year old William had to have a canine removed after an attack by another dog left the tooth sticking out at a right angle. A year later he needed the next tooth back removed. The vet wasn't sure if it had been damaged at the same time as the first but showed no signs at the time, or if it had just decayed. Apart from that his teeth are pretty good for his age and as far as I can tell none of them wobble.