- It doesn't matter.
- It won't matter.
Where is correct? Still confused when I use it so tell me good people where is the correct what should I talk
Either might be correct depending on when it does or does not matter, as @juhasz explains. "Doesn't matter" (does not matter) is present time. It does not matter now, at this present time. "Won't matter" (will not matter) is future time. It might (or might not) matter now, but it will not matter at the relevant time in the future.
Example 1: "Paint the table black or white. It doesn't matter." I don't care what color the table becomes.
Example 2: "Purchase the apple today or tomorrow. It won't matter." We do not need the apple until 3 days from now, so it does not matter when you purchase the apple so long as it is before 3 days from now.
Those are silly examples, but should show that the difference as to do with time (current or future).
The use of "doesn't" and "won't" follow the same rules in this context as in most other contexts:
Doesn't refers to the present tense and sometimes to an ongoing state.
"He doesn't want to go out." - In this moment, he has no desire to go out.
"He doesn't sing." - As of now, and until further notice, he is not singing and will not be singing.
"It doesn't matter." - This choice has no important consequences right now. If you make the same choice tomorrow, this may no longer be the case.
Whereas won't is always about the future.
"He won't want to go out." - If you ask him to go out (which you have not done yet), he will say no.
"He won't sing." - He may or may not sing at various times, but at some specific future time he will refrain from singing.
"It won't matter." - Regardless of whether or not it matters now, in the future the outcome will be irrelevant.
Both phrases leave a lot of room for interpretation and need context to be completely clear. Consider the difference made by context in these examples:
It doesn't matter how hard I try, I can't lift a truck over my head.
I am working from home today, so it doesn't matter if I wear makeup or not.
Eat as much vitamin C as you like, but it won't matter. Vitamin C doesn't prevent colds.
Avoid Main Street today because traffic will be heavy. Tomorrow it won't matter which street you take.
In both sets, the first example communicates a constant and permanent status (it will never matter and has never mattered), while the second only applies to a specific situation.