grey screen

Unplug the system, remove the base cover and disconnect the battery from the system board.  Reconnect the battery and replace the base cover.

Hold the D key through powerup.  A series of self-test screens will appear - are they clear or similarly faulty?  If they're clear, you may have to disassemble the system and re-seat the ribbon cable that connects the display to the mainboard.  If the PSA diagnostic shows the same fault you've seen before, replace the display panel with a new one.

The gray screen appears to be cause by an out dated / corrupt Video driver. Lately, there have been a lot of complaints about gray / vertical screen. You're able to get into windows ?

Note: I'm hoping one of the forum Dell reps see this thread and report this problem to the Dell team.

@AdrianG001  Did you miss the part where OP Said "I accidentally punched my laptop" 

@Nadz727  Depending on your boxing skills if you are a PRO or not,  : You will need an LCD replacement.  Please check if there are visible signs of Damage on LCD by turning it off and using a flash light. Dell support will not replace LCD if, you don't have a Complete care(accidental damage) warranty on the machine. 

If you are good with a screw driver we can recommend a part which you can install by yourself. 

This grey screen comatosis sometimes (mostly after some time) but is followed by a long period of system hanging to "system interrupts"...

I leave it to self-recover and check what is displayed on my Task Manager...