This is urgent. Hopefully the ER doc gave you some antibiotics. If not, get some from the dentist today. Call up and tell them it is an emergency. Cellulitis is nothing to trifle with. Don't worry, antibiotics can do wonders and in a few days you'll see a huge improvement. Apply cold and hot packs, alternating. Let us know how it goes. Hopefully by now you're on the mend. I wrote an answer just in case you haven't seen the dentist yet.