1. Not anything important.
I wanted to see him before he left but it's no matter.
2. It makes no difference; regardless of.
She was going to be a singer no matter what difficulties she met.
He had to get the car fixed no matter how much it cost.
No matter what you try to do, it is important to be able to speak well.
You can't go in no matter who you are.
Mary wanted to get to school on time, no matter if she went without breakfast.
Source: A Dictionary of American Idioms