I have a blister...

I usually pop'em, but if that's big maybe you should consult a doctor because that swelling can be a breeding for bacteria Not treated carefully, it can result in some days in the hospital getting injected with antibiotics. After you pop it, if you do, you might want to keep your foot a good 20 mins a day in salty water or buy some gel like "Lamisil" (that's how it's called here) to counter the bacteria.

Try not to pop it. The unbroken skin over the blister will keep it from becoming infected. Wear flip-flops. See a doctor if you really can't stand it. Should be gone, or at least bearable, by the time you read this.

You just need a matching one on the other foot.

I pop it but then clean it and cover it with a sterile bandage. Popping it relieves the pressure and usually a lot of the discomfort.

Just use a pin and then carefully push out the liquid inside. Keep the skin over the blister to protect it. Keep it clean!
It will pop on it's own anyway. You might as well get some relief now.

Use the pin at the thick part at the base of the blister.