Could someone pleaseee tell me what happens when nitric acid is added to and iron nail?

I am doing a chemistry experiment on rusting of iron. I placed 4cm3 of nitric acid in a test tube with an iron nail. A reaction took place immediately causing vigorous effervescence and particles from the nail started to sink to bottom and the nitric acid started to turn dark brown also the test tube was very hot. I was confused why this happened. Can someone please explain to me why the nitric acid corroded the nail so quickly.