Going to have hsg on day 8.trying to conceive in the same cycle is there any harm to fetus?

No: The purpose of limiting performance of hsg to first 10 days of cycle is to avoid exposing an existing early embryo from radiation, i.e. Performance of the procedure prior to conception.

Avoid interourse: We recommend avoiding intercourse for 2 days prior and 2 days post an hsg. So if you have regular 28 days cycles you will be able to have intercourse around the time of ovulation. If you have shorter cycles you might have to wait until the next month.