OP, if anything I have more respect for colleagues who just carry on regardless. Anyone who spends more than two seconds noticing is being weird and unprofessional. The less you think about it, the less awkward you'll feel, and the less anyone around you is likely to react or care.

Treat it with whatever treatment works for you, and don't cover it with a bandage or makeup - a bandage will draw questions and makeup on cold sores just looks awful.

Like you said, it's common - so don't worry about it.