changing WordPress blog URL

I installed wordpress and completed the setting, I know its my mistake but accidently I filled in setting>>general setting and this, I mean I just written / blog and saved and boom error came, I tried to go to options again to redo that but it was too late now I am stuck and my homepage looks like this https://hdubuntuwallpapers.com and I tried searching and searching but I am unable to get it back, can anyone help me here?
here is the image what I did https://i.imgur.com/X7YcvVi.png
Help me if you can :/