have you called NHS Direct if you don't want to visit your gp? they will be able to assess the seriousness of the burn.
from what you say, it doesnt seem too serious, but then again I can't see it and i'm not a doctor.
if your worried that it may be a serious burn, then go see your local nurse/gp immediately.
keep it dry and keep it clean - especially if the blister has broken - broken blisters are prone to infections on burns. try not to aggravate the skin by touching the burn or the skin around it either. if you have long hair, keep your hair tied back to it does not irritate and spread bacteria to the blister.