Thank you for your message and the context you provided into this issue, sorry to hear you are having this problem. I would certainly be happy to offer you some assistance. I'd also love to hear more about what sort of customization you were initially trying to make, perhaps I can offer some suggestions to get you on track with your idea!
Anytime you save code changes in your theme files, a version is saved which you can revert to using the "Older Versions" button at the top of the file.
By selecting an older version, you are effectively reverting that code back to an earlier state, so reverting to a version prior to when you made those edits is a quick way to resolve this. We have a helpful guide that will walk you through the process step by step.
If you are still seeing that coding on your product pages after this, please feel free to reach back out here and let me know what Theme you are using and I would be happy to offer you some further ideas.