Hi there ~
I understand your concerns. I believe that the red swollen pus filled blister
on your finger is an infection of the layer of covering of the tendon in your finger or the outer part of it. It is easily drained by an incision and you should visit with a surgeon as soon as you can. I hope this helps. However not having an expert do it may make it worse and you might need to visit multiple doctors and take multiple medications if you do not take precautions now and visit with a doctor.
I hope this helps. Take care and have a lovely day!