It hasn't popped yet. When it does, out comes the disinfectant.
I never understood the neurotic, paranoid tendencies of most people to douse every common minor surface wound with peroxide, alcohol, Neosporin, or some other type of "anti-biotic", when the most powerful, innately intelligent anti-biotic substance known to man freely flows throughout every inch of your body as BLOOD.
The fluid accumulated under the blister is there for a reason, and it is doing exactly what it has evolved over thousands of yours to do.
Void of a compromised immune system or vascular condition, best to just leave it alone.
When it is ready, and the healing process has run it's course, the outer surface skin of the blister will weaken, rupture, and shed to release the remaining fluid, exactly as intended.
The human body if far from stoopit............ surprisingly........ even Marty's.