How can I fix my Mac's internal speaker volume button?

I’m having a problem here, there was a day I plugged in my headphones into my Macbook Pro and when I unplugged it my Macbook Pro’s volume button isn’t working how it’s suppose to.
I have to go to Preferences > Sound and then adjust the volume from there and this is still happening. The only time the internal speakers volume button is working like normal is only when I restart my Macbook and that’s just a nuisance to restart it every single time.

So I was wondering what’s wrong with it and how can I fix this problem?