Will it ever pop or is it getting worse?

my son is 4 months old he had a ct scan on friday and they couldnt put an iv on him because he is to chuncky and so they use a microscope light to find a vein under his foot and the doctor did it for to long and burn his skin under his foot so now he has a blister and since friday the fluid inside has been increasing does that mean it will pop anytime soon or is it getting worse, it doesn't really bother him much he acts his normal way i just want this to be over.