Sanded paint back to body

Arrgghh...need help :(

I had 3 coats of primer and 2 coats of paint on when I realized that there was a nice scratch in the paintwork, I let the paint dry over 24hrs and sanded it today.

The only problem was that the sratch was deep and I had to sand all the way back to the body to get rid of it.

Now, do I use primer on the whole car again, or can I get away will just priming and sanding the affected area and reapplying more paint coats?

if the body color is not very different from the color you're paint(as in, it will bleed through) I would just spray the area with the color , depending on the size of the area the primer was removed from.

heres a good way to look at it, you're gonna have to redo it anyways if you dont spray it right? so you might as well spray it to see how it looks.......if its bad just remove the paint like you would originally