The blister from my sunburn popped in my sleep last night what do I do?

A couple days ago I got sunburnt pretty bad although I just thought it was first degree. Well here a couple days later, I start getting some blisters popping up. I didn't really know I had any until I went to bed last night. So I just got up and put a band-aid on it since it was relatively small (I've never had blisters from sunburn before so I didn't know what to do and my dad was asleep.) and went back to bed. So I was up in excruciating pain this morning and find a long line of the dried liquid from it going down my arm and 2 or 3 times bigger than it was when I went to bed. And I also have three or four more open blisters by it. What do I do? How do I treat this? And of course this would come up the day I have a date :(