SSL encryption: a domain for a seedbox, a good idea?

Hi all,
I 'm a newbie and discovering all the marvellous features of QuickBox.
But my browsers make problems accessing , telling me that my ssl certificate is not valid anymore.
I can get a valid ssl key with let’sencrypt , if I register a public domain, am I right?
And if I register a domain , some may find my seedbox via google and other search sites: is it a really good idea to have a public domain , if only I have to access to my seedbox?
thanks for your advices !