Accidentally sat on a stove. how long will it take for the blister to heal?

You have a 2nd: Degree burn if you're blistering, and these are very susceptible to infection. Don't play with this yourself. See a doctor!

Simple Treatment: With injury to our skin, inflammation occurs which means the area becomes red, warm, tender and with swelling. Swelling occurs under the skin layers and causes them to bulge creating a protective fluid cushion called a blister. As the area heals, the fluid will be resorbed or when no longer needed, the blister opens and it drains. This should take about a week. Keep it covered and protected.