Oil pressure light

[Tom35]

Oil pressure light comes on when engine is hot and but goes on and off when reving 

[Tom35]

Nissan qashqai +2 2.0 diesel 

[Trevor]

I would definitely get an oil and filter change as soon as possible to start with

[Tom35]

Already done the oil and filter  and also changed the pressure switch 

[Trevor]

Only other thing I can think of is an engine flush and the oil refreshing once more.
A garage should be able to take readings of the oil pressure to determine if it is up to scratch, if not then flush the engine.