sounds to me like a coldsore.
I am extremely prone to them and they usually start off as a cluster of small spots/blisters and will then turn into a scab.
They can last up to two weeks and are highly contageous so if you do have one then you wont really be able to work unless you maybe dont include kissing or OWO.
Good tips to get them to clear up a bit faster are:
Tea tree oil (the pure stuff, not the aromatherapy oil stuff. You can get it in chemists and some big supermarkets)
Zovirax can help a bit, and Compeed coldsore plasters are handy as they stop the coldsore being crusty and sore,
A supplement called l-lysine is excellent to take every day to stop them from coming back in the future (I havent had one for months since I started taking it and I used to get them at least once a month).