Is it ok to masturbate 4 days after breast augmentation surgery?

You should get clearance from your own surgeon. I don't see a particular problem with this provided the sexual activity does not involve your breasts.

Each surgeon has slightly different recommendations. In general I advise my patients to avoid any activity that raises the heart rate or blood pressure during the first 3-4 weeks after surgery, as this is the period at highest risk for having a bleeding problem. I hope this helps - good luck!