Hello there! Please follow the steps below.
Turn off your maachold down the ‘Command’ + R’ keys on the keyboard during the start up process when you see the Apple Logo you can let go. When the machine boots eventually you will see the OS X Utilities screen., select the Disk Utility and then select Continue. Then in Disk Utility select Macintosh HD in the left column, if there are two or it is named something else choose the first indented item, and then select Verify Disk on the right. If that is OK in green type then select Repair Permissions. If it is not ok let me know. If that is ok quit Disk Utility and then select exit installer. check to see if issue is resolved.
if that does not work try the following
• Turn off your Mac.
• Turn it back on and immediately hold down the Command(Apple) and S keys together for 10 seconds to boot into Single User Mode
• When you see the text prompt, type in the following terminal commands to create a brand new Admininstrator account (hitting return after each line). Also, note down the spaces between the commands, like a space between mount and -, space between -uw and / etc
mount -uw /
shutdown -h now
After rebooting, you should be able to create a brand new Administrator account. Then in new account, goto System Preferences > Accounts, select your old account and change/reset the password. Then logout from Apple menu and login to the old account with the new password.