Girl I have the same problem. I went to the beach in corpus christi. I had it pierced before but it rejected then I got it repierced nd thats when I went to the beach, about 3 days later this little pink bubble blister popped up in the middle. I went to the people who pierced it and they said to clean it with dial antibacterial soap and rli hot water until it burst so I did nd all kind of yellow goo came out. They said it was from my recent piercing you see? So to make it go away they said take a q-tip and apply direct pressure for like 3 minutes everyday and wash it twice a day. Also not too much on the sea salt soaks. It could be a bit much. Just do those two things and put a towel in hot hot water on your tummy every day too. It has improved dramically =] it could be about a week or so for it to completely go away though. Good luck! Hope this helped! =]
Body piercings in areas like your naval which may harbour moisture are prone to infection. This "bubble" could be early signs of an abscess due to infection under the skin and could lead to serious condition if left untreated. Is the area red or warm to the touch? How long ago did you have this done? Piercings are ideally kept clean and dry which is rather hard to do in the naval. I suggest that you have a professional look at that immediately.
It sounds like a combination of infection and irritation from having it ripped out and the new one put in. Clean it twice a day with sea salt solution and if it doesnt improve go and see a doctor.