sounds like it could be slight shock e.g. when you get hit on the head and you get a bit "dazed". I think the first thing you should do is get the finger checked out as steel landing on a finger is never good, while there, mention the flashes, it's always better to know there's nothing wrong then to falsely presume
has he ever hit his head in his life.Or he might have to see a Phycologist Doctor.
Welcome to the MedHelp forum!
This can be due to extreme panic created by the incident. Hitting the finger with heavy iron could have resulted in an exaggerated vagal response. It can also be due to a head injury (did he fall because of the impact). Hence get this evaluated by a doctor and an eye specialist immediately. Take care!