First you should know that the Apple factory hardware in many MacBookPro's do not reliably support a 6G (6Gb/s) Solid State Drive or Hard Disk Drive in the optical bay, so if you're using a new hard disk you will encounter disk corruption and many strange problems.
Since you did a clean install the new user UUID for your account no longer matches what was there before. All the data on your old disk is protected using these old user UUIDs. You should have performed a Migration to create your "new" user account(s) and move over any files. You should be able to still do this from a Admin user account and the Migration Assistant application in the Application > Utilities folder.
If you're an admin user you should be able to Get Info on the drive and Ignore Ownership on it. (Click the lock if required.) This will allow you to access the files but now you won't have any permission checks to protect who and what processes can access the drive. But it will allow you to copy them off.
If you use Get Info's Sharing & Permission's you can add your new user with permissions to access the file(s) but this retains the old owner unless you also select the newly added user and use the 'gear' pulldown to "Make the owner". You'll also probably want to "Apply to enclosed items".
It may just be best to disable owners on the volume, copy the files off, reformat the drive and add back your files as the new user. This will get rid of a lot of "gremlins" that can persist in these situations.