When do I remove the cotton ball from a dental surgery?

You should not need to bite on anything after dental implant surgery.  specially if any type of bone graft of tissue graft has been also performed....  Surgeons usually achieve good hemostasis using stitches.. To prevent bleeding you should avoid using Straw, and you should not spit / smoke

Removing the gauze or
cotton should be done after bleeding has stopped. This is usually well within
an hour after your procedure. Keeping the compress in place before then helps
to reduce blood flow and promote clot formation. If your site continues to
bleed, you need to check back with your dentist. Otherwise, a painful condition
known as a dry socket may develop.

30 to 45 minutes is enough. Drinking chilled water immediately after removing cotton ball is suggested.