I keep forgetting how to fix this error, so I am writing about it; If you happen to come here out of frustration; I only promise that it solved my problem, and if it doesn’t work for you too, sucks to be you right now; I have been there.
You are getting this error, because the pid file was deleted. This happened for one of two reasons, you renamed your machine or for some reason unknown to everything holy you decided to manually restart mysql.
Here is a snapshot of the error.

What you need to do is go to the directory mentioned in the error. Delete the *.err file and create the file it is complaining about in the error.
Then restart the MySQL server. This fixes this ridiculous issue with MySQL on OSX.
If this didn’t help you, let me redirect you to google hell click here.