HMD have left the keys to the bootloader in the lock on your 7.2. This is not a security risk, because Google and many other companies do the same for their phones. Unlocking the bootloader allows you to flash a different variant of Android and maybe other OSes in future if you wish to.
However, HMD have decided that they don't want you to have this freedom of choice and will remove the keys in a future update.
If you read all that and think it sound cool but you don't know what all the technical jargon is then do some more reading around the web to educate yourself before doing it.
If you read it all and think it all sounds way to technical and scary then you don't have to go any further - it's your choice.
And that's what this is really about - choice. HMD have accidentally given you the choice, and now then will take away that choice, and by doing so they will restrict your freedom to do with your device what you want to do with it.
Does that sound fair?
If not, then reply here to show HMD you want to keep that choice.
PS - don't ask me for help unlocking the bootloader, ask in other threads.