Accidentally hit my head 12 days after my FUE hair transplant, blood came out. Did I loose many grafts? (photos)

At 12 days, hitting your head with bleeding may have cause some graft loss but by that time the grafts should have been secure unless you had heavy scabbing present at that time

At 12 days post-op, you should be safe. You may have dislodged some grafts, but I would say it is unlikely. If the area was not cut enough to leave any scarring after it heals, you should not have any lasting damage. It is always best to follow up with your doctor though to have it looked and confirm.