How long to have sex after a testis biopsy?

Depends on pain: There is no contraindication to having sex -- although there are two caveats: you may have blood in the semen (ejaculate) -- but, if you don't look, you won't see it; you may have pain in the scrotum or be sensitive. I suppose if you are not too vigorous or bouncy, you should be fine. If there is a suture, you cannot get it wet until they have been removed or it has healed -- so think about that.