You can open the workflow in notepad or notepad++. You will see that at its heart, its just a big long XML document. Go the line and character in the error. You should see an XML node without a closing tag or missing a > or something. Correct the missing node or missing character, then save and and try opening it again.
This happens to us a lot, we we frequently add new tools or delete tools out of existing workflows.
@YPatil01 If the workflow has macros(standard macro) in it, the issue may be because of macro. I faced similar error message while trying to open a workflow(in lower version) when the macro was developed in higher version of Alteryx but the main workflow is in lower version.