this lock is set in below table so you can unlock by update query.

SELECT [UserName] FROM [vw_aspnet_MembershipUsers] WHERE ([IsLockedOut] = @IsLockedOut) ORDER BY [UserName]

Also below are the code behind code is also usefull to unloack your user.

 Dim mu As MembershipUser = Membership.GetUser(ddlLockedUsers.SelectedItem.Text)

        mu.UnlockUser() 
        Membership.UpdateUser(mu)