I get horrendous cold sores! I keep a bottle of surgical spirits in my bathroom and decanted some into a little container I keep in my bag. I just dab it on every hour or so. i find mine heal faster if they are clean and dry.
Lysine, zinc & B12 are good at preventing them and reducing the lengh of the break out but dont relief straight away. I take a small overdose of the Lysine the moment I get a tingle and take a little more than they bottle recommends until they are clear.
Lysine is only safe in small quantities in pregnancy though. I think its 500mg twice a day from memory but I would check with the pharmacist!
Good luck. Coldsores are bloody horrible x