I, too, am an RN and I agree with my colleague above. I would not drain a blister, especially a deep one. Blisters are the body's response to friction and trauma and intact skin is always your best defense against infection. Leave it alone and get rid of the flip flops and you'll be fine. If you find you're having a problem with it then go see a physician.

Oh, and as any OR nurse will tell you, you'll never sterilize anything with alcohol.