I Have A Friend Who Injected Cocaine Into His Vein

I have a friend who injected cocaine into his vein and he thinks he missed. The top of his hand is where he did it and his hand is very swollen only on the top of it and it sends a sharp pain all over the top of his hand and into his wrist everytime he moves his finger/s. Can you say what the problem is, if he needs to go to the doctor, or when it will go away?