Probably too late
Sorry to hear about your outbreak.
You don't say whether it's oral or genital, but that probably doesn't matter. Unfortunately, you are correct that it's pretty much useless to start anti-herpes treatment more than 2 days after start of an outbreak. unless it is unusually severe, e.g. if new blisters/sores are continuing to appear. At ths point, just keep the area clean and dry.