Forgot cover screw: what are my options?

It depends on how much primary stability you have. If it went in nice and tight and If it's within a few days, I'd expose it and place the cover screw. Do not tighten the screw much at all. If you did not have much primary stability, I'd simply leave it be and expose it after 3-4 months and place the healing abutment.

I had the same experience where I forgot the cover screw. Later the implant site got infected due to the hole in the implant. But I would wait until surgical phase it past because if you open up the implant site, you are messing up the GBR and implant as well. Later if implant integrates ok, then you can put cover screw when uncovering. If indeed implant site is infected, then that is sure signal you need to go back anyway. So wait till heal. Go back when only if problem.

I would leave it alone as well. I have had more than on patient return to the office, or who had the implant placed somewhere else, and lost the healing cap more than 6 months prior. Nothing ever seems to grow into the abutment well. So I wouldn't worry about it

i completely agree with Dr kwan M Lee, open the site only if there is problem otherwise wait till implant integration

i have no idea how much bone is grafted around the implant. But , if you have used a membrane it should take care if it is non resorbable membrane then not to worry if it is resorbable membrane then best is to open it up only on the crest of the implant area and put the cover screw so bone will not grow into the hollow chamber .

I think the future of method of the implant will depent on the material and method of GBR if the implant is covered with non resorbable membrane most probably there will be no problem if not soft and hard tissues may seal the lumen and there is always a great risk of destroying the threads while trying to clean the lumen.So please take into consideration my humble thoughts before going on your treatment.Good luck.