Definitely go to the dentist to get it checked out, and you're lucky to have gotten an appointment so quickly. Apart from the blurred eyesight and headaches, I had similar symptoms a few years ago with a number 6 upper tooth that was deeply filled. I kept getting a dull pressure in my cheek bone, a blocked and continuously runny nose, some pressure under and around my eye, especially when I bent down/leaned forward or did exercise. I then got a pain in my tooth, so I went to the dentist, who told me it was just that I was putting too much pressure on my tooth when eating, so he ground it down a bit. This went on for about 3 or 4 months, with the same result and he told me it couldn't as bad as I was describing because the tooth was root filled.
The pain got worse and worse and eventually one evening when I sniffled (no more than usual) I got a searing pain that moved up from below my cheek bone (where the top of the tooth is in the jaw), around my eye, into the bridge of my nose and my nose started to stream. I blew my nose and the most awful substance (gunky and foul smelling) came down through my nose - it turned out it was pus from an abscess that had been on my tooth for well over a year, but which my dentist failed to diagnose.
Cue my return to the dentist four days later (first available appointment) who told me it was my sinus. Visit to doctor later that morning who said it definitely wasn't as I had no major sensitivity around my sinus, but gave me antibiotics anyway because I had such a bad infection. Returned to dentist 3 weeks later (next available appointment) with my abscess still draining and he told me he'd re-do the root filling for me, but that it'd take between 5 and 8 visits.
And all of this took place when I was trying to study for my finals! Somehow managed to struggle through my assingments and exams and then decided to find a new dentist and found one who was great. I described my sypmtoms, he checked my tooth and gum and the teeth around it, tapped the tooth, said that there was still infection in it (about 3 months later after 2 doses of antibiotics), x-rayed my tooth, told me exactly what happend and why the abscess had burst in the manner it did, showing me on the x-ray, and told me that he'd put in a root filling. I asked him about replacing the current root filling, but he told me that my tooth wasn't actually root filled, it just had quite a deep filling in it and showed me the x-ray of the normal filling because I told him my dentist had said it was root filled. Anyway, he root filled the tooth in 3 visits and didn't hurt me once (my old dentist didn't always give me enough anaesthetic, even when I told him it hurt during the procedure!). That was about 6 years ago and I've had no problems with it since (and just got it checked yesterday, so cue a very happy customer
Best thing is to get your dentist to check it. I really regret not finding a new dentist sooner because my health suffered hugely because my body was so tired fighting the infection all the time. Antibiotics will help fight the infection so that your dentist will be able to treat the tooth once the infection has cleared up. Don't let it drag out. Best of luck, and hopefully the abscess isn't too bad!