Thanks for the query.
I understand your concern.
If during masturbation you are inserting any object into vagina, that can damage the hymen or injure the vaginal walls and can lead to bleeding.
By avoiding these things bleeding can be prevented.
If bleeding occurs even after this, better to consult your doctor once and get examined to rule out abnormalities like vaginal septum, polyps etc.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.