Categories not saving

I’ve installed WordPress locally on my Macbook Pro and I’m using Xampp for the server part of it.

All was working fine until I realised that it’s not saving categories I add. After I add them, they appear in the left in the right but as soon as I navigate away from that page and back to it, they’ve gone.

Also, I can’t access PHPmyadmin, as I get the following error:

SQL query:

SHOW PLUGINS

MySQL said:

#1 – Can’t create/write to file ‘/var/folders/zn/ch10hp092m75z51hxjj2496c0000gn/T/#sql165_39_0.MYI’ (Errcode: 13)

I’m guessing they’re related.

Categories were saving previously and the only thing I can think I’ve done since is enable FTP in Xampp and install a new theme (although haven’t activated it).

Any thoughts on what’s wrong would be much appreciated.