wrong link in wordpress URL text box so everything redirecting to wrong place

HELP! I am new to wordpress and was trying to update my ‘general options’. In the wordpress Address URL text box, (where you are meant to enter the location where you’ve installed your WordPress blog software, I seem to have entered the wrong filepath to my wordpress blog. Now my site is not even loading and all the links keep redirecting to a broken link error 404 – which means I can’t even log in to change the mistake.
Please can anyone help? Also the wordpress blog is now all in HTML? I have no idea what’s happened!!!

Thanks and apologies in advance for lack of WordPress/ computing knowledge.