The answer of this riddle is 7.
Explanation :-
There are 7 candles lit and if I blew out 2 of them , I still have 7 Candles 5 lit and 2 unlit.
But still there is catch, if those 5 candles are lit longer, they will melt and we will be left with 2 candles.
So, Depending on the time when we count the candles answer would be either 7 or 2.
Since, in the riddle it is not explicitly stated the time, answer is 7.