I've had intermittent tingling on a part of my upper lip for 48 hours, nothing else. if it were a cold sore, would it already have erupted by now?

Up to a week: Sometimes we are surprised to find that it can take even longer for a cold sore to erupt. Sometimes it is something else. Tingling can be sign of something else in people including food allergy. Although oftentimes there is rash that accompanies. If you have had cold sores before you could consider an OTC product like Abreva to see if this helps.

Poss cold sore: This can signal the emergence of a cold sore. Hopefully none will appear. Watch the area closely. If the tingling persists beyond another day or two or gets worse schedule an appointment with your doctor to review your overall health. Good luck, I hope you avoid the cold sore!