So where does it go from here? If anywhere?
What happens next really depends on your employer. If they don't think it was a problem, then you are probably good.
If your employer feels there is a problem then ask your employer what happens next (well ask either way and getting the response in email is nice).
I had a coworker complain to HR about me, but it was also a part of a campaign to file complaints against a laundry list of people and my employer did not feel the complaints were valid. They were very minor complaints that didn't even make sense on the most basic level (like misnamed me several times, identified me as someone else, identified tasks I wasn't even responsible for, and then they would say I helped them with the things they previously complained about).
I was very clear with HR about things. Followed up with an email to HR to get what I said in writing.
Then I was just very careful around that employee, emails were very clear and detailed, I did everything I could to not be alone with that person.
Eventually that employee left, tried to sue the company (for entirely new claims unrelated to me), had case thrown out and it was ok from there.
But every company is different so who knows what might happen.
If you feel things start to get confused... contact a lawyer who can give you advice. Plenty of lawyers out there who can offer advice for free or cheaper for just a bit of their time.
Keep in mind only your own lawyer is there explicitly to help you and will have your best interests in mind.
No matter what your company says HR is there to protect the company, NOT you.