S
PIP and Universal Credit are separate benefits, the former is awarded to help with the additional costs that a disabled person can have, UC in the context of disability is an income replacement benefit for those unable to work due to their disability.
Before you report a change, can you reasonably score the extra points that you need for a higher award? If you can't then the DWP are unlikely to be bothered by your failure to report a deterioration in your conditions.
If you do report a change, then do so in writing to the DWP office dealing with your claim, if you can afford to do so, send it by a Tracked post so you have proof of delivery.
You will need to have had the new limitations for at least three months before a revised award can be made.
Reporting a change will result in a new PIP2 form being sent and almost certainly a face to face assessment, the resulting Decision will supersede your existing award, whatever it might be
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
