Hello
I understand your concern.
Black toe nail can be due to trauma or
fungal infection of nail because of underlying cause like
diabetes.
In your case,the cause seems to be of trauma as it followed after you had race few days back.Black colour is due to minute bleeding spots at nail bed due to
blunt trauma.Yes,you will get a new nail after this one falls off.
You just need to let the nail fall of it own.
Analgesics like
acetaminophen twice orally for 3 days for pain relief.
Wear close fitting shoes especially while running.
keep the nail clean and dry.
If the new nail growing is still of black colour,or colour spreads to surrounding skin,consultation with
dermatologist is needed.You may need local examination and certain blood investigations to rule out other possibilities I mentioned.
Hope this information helps.
Feel free to ask any more query if you have.