damn that sucks, yeah my brother had gotten really bad blisters on his lips that same time that I had went when I got super burnt (I didn't get any blisters on my lips) it took him a couple weeks to heal, but his lips returned perfectly to normal. But my personal guess is either way the sun will help your condition. I did want to ask if you used any type of sun screen or anything? Because I wasn't using anything. Although toward the end of the day when I was really starting to feel the burn I bought some sunscreen, but after that point I haven't used it since. I think the Vitamin D or whatever else is created from the sun has a lot to do with it as well, so letting the rays in as much of the body as possible probably helps as well.
But I wouldn't worry whenever I went out my lips didn't feel and look better until the following day, and that was a couple months into the consistent sun. Even with blisters I still believe it will help you though, however I would ease off the sun a bit at this point until they heal.