Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services if bleeding is accompanied by fainting, severe dizziness, confusion, breathing difficulty, or marked weakness.
Arrange a medical appointment promptly if you develop unexplained vaginal bleeding, especially after menopause or after sex.
Persistent unusual discharge, a vaginal lump, pelvic pain, or new urinary or bowel symptoms also need assessment.
Seek urgent medical help for heavy or uncontrolled bleeding, severe worsening pain, inability to pass urine, or signs of infection such as fever with feeling very unwell.
And for anyone, someone who:
The article also says
If you have been treated for vaginal cancer, report new bleeding, ongoing pelvic or back pain, leg swelling, unexplained weight loss, or changes in bladder or bowel function.
These symptoms do not necessarily mean the cancer has returned, but they should be checked.
Every sign above is quoted from the sofidex article on Vaginal cancer. If you are not sure, err upward — it is always reasonable to be checked.