What Causes Yellow Discolouration Of Nail Due To A Injury?

Hi, i recently smashed my finger in a car door, it turned blue but the nail cracked when i smashed it so the blood was oozing out by itself gradually. The blood has now disappeared but the nail has turned yellow and is coming off from the cuticle upwards. The nail is also a rotten smell and i am scared that it is infected. Wat should i do?