I am using this nexus dock, and i want to protect my family members kids change the settings like adding new dock etc, with a password is it possible?

Unfortunately, no. The only thing you can do is lock the icons, so they cannot be accidentally moved via drag & drop.

The OP should never let kids use his account (or for that matter other adults) and instead create separate accounts for them in the first place. Then he could use his administrator account to go to the Nexus executable and edit its properties, taking possession of it as administrator and only allowing full access to his normal user account, while barring all others. Simple as that.

Yes, that would be ideal as Nexus settings are also per-user.

However, not everyone is savvy enough to know how to create and manage different Windows user accounts - plus, it does not solve the problem of children messing up their current dock configuration (although this can be somewhat alleviated by setting up the dock as you want then immediately making a backup of those settings in the General tab of Preferences - if the children later mess it up, recovering will be as easy as restoring the configuration you previously saved)

Well, that sadly is all too often the case. Yet, even just plain old common sense ought to tell everyone that the first thing to do with your computer is explore all the different options it offers in places such as settings etc. and, indeed, configure the hell out of the damn thing to make it safe and as private as the OS lets you (not a lot! In fact, if using Windows or macOS it sends an incredible amount of data back to MS or Apple respectively unless you block that by careful configuration of a firewall, and even then...) Anyway, the point is, especially if sharing with other users, then you really absolutely need to learn to create and manage user accounts. (I'd bet money that a very sizable proportion of computer illiterati run their machines in the default admin account forever after!)

Of course, much the same common sense should always be applied to any app that is used. If people did we'd probably get only a tiny few percent of the cries for help we see here!