Update: Blood Filled Boil/Blister Inside Cheek

Hoping that 2nd post's a charm, because the bubble thing got worse overnight. 1st pic is current, 2nd is from last night. I'm 24F, no smoking or alcohol, and only physical ailment is GERD.

The bubble is not in the path of my teeth, so I'm not biting there. I admittedly did squeeze it a little before taking the picture from last night (2nd one), but it only swelled, nothing came out. There's no apparent thing that caused it; it seems like it grew suddenly.

My questions are: What is it? Is there a safe way to pop it at home, or do I have to leave it and let it drain on its own? When do I need to see my dentist?