Can a cold sore be just one bump or is it almost always a cluster of small bumps?

Oral herpes: Clustered bumps are most common, but single lesion is possible. More important is how the bump changes over several days. Typical herpes starts as red bump(s), within 1-2 days become blister-like with clear fluid, then over a few days pimple-like (pus), open sores, and scabs; and healing over the next week. Best Rx is a single large dose (2 grams) of valacyclovir (Valtrex). Discuss w/ your doctor.