'You've been signed in with a temp profile' message

Hi, new to forum, hope you can help.
Win 8.1.
Two users on this PC, myself as administrator and my son. He is getting the 'temp profile' issue. My profile is ok. I have seen the 'fixes' but haven't tried yet. As he has not long purchased his own pc and there is nothing of any importance he has saved on this joint pc, no files or photos, they are either saved on sticks or on clouds, can I just delete his profile or user account? Will it affect anything? Will it delete the 'proper' account or this temp profile? Or is there a way around this? Would this need to be solved before an upgrade to win 10? A lot of questions I know.

Thanks
MartiniMan

If you son has his own pc, I would just simply delete his account and that will be the end of the "temp profile" issue.
After that, run a system file check ( sfc /scannow ) to make sure your system is in proper working order.