I wish I could attach pictures here. It would make it easier to show. However, it is in the inner arch, near the heel. Never tried to drain it. Just left it. Is there a less gross sounding way to do it? Needles aren't my thing! Can I get some sort of dehydrating pad from the store? Like a wart removal pad or something?
It sounds like a blister has formed. Have you ever tried to get it drained or tried to drain it yourself with a syringe? Or as the vast majority of the people would do, just stick it with what ever needle they can find.
Also where is the "bubble" located on your foot?