http://www.webmd.com/skin-problems-and-treatments/guide/understanding-blister-treatment
Understanding Blisters - Treatment
What Are the Treatments?
Most blisters caused by friction or minor burns do not require a doctor's care. New skin will form underneath the affected area and the fluid is simply absorbed. Do not puncture a blister unless it is large, painful, or likely to be further irritated. The fluid-filled blister keeps the underlying skin clean, which prevents infection and promotes healing.

If you have to pop it:

Use a sterilized needle or razor blade (to sterilize it, put the point or edge in a flame until it is red hot, or rinse it in alcohol).
Wash the area thoroughly, then make a small hole and gently squeeze out the clear fluid.
Apply a dab of an antibiotic ointment with polymixin B and/or bacitracin to help protect against infection. Use caution with ointments that have neomycin in them because they are more likely to cause an allergic reaction.
If the fluid is white or yellow, the blister may be infected and needs medical attention.
Do not remove the skin over a broken blister. The new skin underneath needs this protective cover.
Look for signs of infection to develop. These include pus drainage, red or warm skin surrounding the blister, or red streaks leading away from the blister.

How can I Prevent Them?
Wear work gloves. Jobs you do only occasionally, such as shoveling snow or raking leaves, are great for raising a blister or two.
Break in new shoes gradually and put petroleum jelly or an adhesive bandage on areas that take the rub -- before the blister happens.
Wear socks that have heels instead of tube socks (they bunch up and cause blisters).
Polyester or acrylic fiber socks are good low-friction choices. Because they don't breathe as well as natural fibers, however, you should wash and dry your feet after wearing them to prevent athlete's foot.