Hello,
Due to the impact your friends nail has discoloured, it’ll take a few weeks to completely resolve. If there is any pain or swelling or districted movements of that finger, please consult me viz chats.
Next Steps
It will resolve by itself in a few days/weeks depending on the impact.
Health Tips
Giving this area a combination of cold and warm water dip could help, this could help better circulation of blood and resolve it faster.