What Causes Mild Headaches, Nausea, Vision Issues After Hitting Top Of Head?

I hit the top front part of my head on a heavy peice of metal this past saturday. Aside from the pain from the hit I felt fine saturday and sunday. On monday i was extremely nauseaous for most of the day constantly on the verge of puking and same thing on tuesday with minimal headaches on and off. its now wednesday and i continue to have mild headaches and slight nausea but noticed this evening that the vision in my right eye is way off especially is darker settings. i thought that i may have a slight concussion originally but am now more concerned