Mac reinstallation problem

Hello guys, I was having some problems with my MacBook, it says incorrect password whenever i type in my password ( now it wasn't that the password was incorrect because one time the password worked but when I turned off my mac and try restarting, the problem continues). After experiencing this for some time, I cleared my disk using disk utility and reinstalled the os. The install completed but when mac doesn't startup, I'm seeing something about system uptime in nanoseconds. Please how do I go about this ?