Thanks for posting your query.
From the information , you have provided , you have experienced what we call as post coital or contact bleeding.
Whether it occurs after penetrative sex with a partner or self , its the same symptom and usually the causes are similar.
It may be due to dryness, excessive force (traumatic) or due to an infection in the
cervix
( commonly chlamydia which can spread through sexual contact and shared toys) or due to a growth on the cervix (very rare).
Is time to meet your gynecologist, have a full check up and
pap smear if you ve never had one or due for one.
If the cervix looks abnormal your doctor may suggest
colposcopy (special camera test or cervix) and biopsy(testing a small amount of tissue).
If all is well, its advisable to consider having
HPV vaccine to prevent
cervical cancer.
Hope this help,
All the best. Take care.