Hi, I'm Dr. Heindel, I'm going to try to assist you with your issue.

When you say "bubble" I think of a cyst. Does it seem painful? Is it red and angry (inflamed or infected), or simply flesh colored. When I see a cystic structure, I always want to put a needle in it. Sometimes it's just clear fluid that leaks out and it goes away. Most cysts are NOT painful and dogs tolerate the needle insertion well.

If you aren't comfortable popping it, you should make an appointment to get it examined. Don't be surprised if your vet inserts a needle into it :)

I would not panic - this doesn't sound like anything very urgent. If you can pop it yourself, then just clean it with bactine over the next 3 days and it should heal. If you aren't comfortable doing that, make an appointment - no rush, this is not an emergency. It could be a number of simple issues, and very unlikely to be something bad, based on your description.

Good luck,
Dr. Heindel