Help. I have a medical question about my 17 mth old daughter.?

My 17 mth old burnt her finger on the iron a few hour ago and I did the right thing by putting it in water and so on but it has gone white and swollen as burns do but when it becomes a blister what should I do then. Im I suppose to burst it with a small needle or just leave it alone and it will burst by it's self and clear up it's self. If Im suppose to burst it am I suppose to put something on it afterwards. I have no idea what happens next. First time mum and first time burn. Please advise.