Hello..I have gone through your question... The blister on the tip of your nose can be the starting sign of opthalmic herpes zoster infection. I think you are aware of the fact that herpes virus is fond of nerves and affect the nerves. The nerve which supply the cornea, lateral aspect of your nose and tip of nose are the same (Nasociliary branch of trigeminal nerve). So blistering on tip of nose can be a starting sign. If what we suspect is right there will be similar blisters which develop in one half of the face without crossing the midline above the jaw bone, which can be quite painful. So my advise is to consult an opthalmologist to rule out a opthalmic herpes zoster infection. Kindly do a diabetic mellitus workup as well as herpes zoster infections are common in diabetic patients. Other possibilites can be 1. Infection of underlying sweat glands/sebaceous glands. 2. Infection of a hair follicle. 3. Insect bite reaction.