As a sole proprietor or single-owner entity, you are generally not within OSHA's jurisdiction (some state programs may cover you, depending on details). You are not an "employer" or an "employee". However, if you are working as a subcontractor to an OSHA-covered entity on a jobsite, that GC will generally be responsible for your OSHA compliance on their jobsite. They need to handle it contractually by requiring you to comply with OSHA rules in their agreement with you, and backcharging you for fines they may receive for your violations. The situation you describe, however, is more of a tort liability problem than an OSHA compliance problem. If you expose anyone else to a hazard by breaking a rule or standard practice that most of the industry generally complies with, that is almost certainly negligent. If someone is injured you can be sued, and the liability may far exceed whatever fine OSHA could have imposed. Since you are not the victim's employer, you are not protected by the worker's comp rules that often limit employer liability for injuries. Good general liability insurance is a must, and it pays to follow standard safety practices even when they aren't enforceable against you.
Obligatory disclaimer: I am an attorney, but not your attorney, and this is not intended as legal advice to you or for your specific situation. This does not create an attorney-client relationship. This is just public discussion of a general issue.