This is a case of having a over harvested donor area. One thing you can do to camouflage the thinning is Scalp Micropigmentation.
The patch could be related to anagen effluvium after donor harvesting with FUEexcision technique, do not panic, it could be temporary and DO nothing yet. I will suggest you to wait 3-4 months for hair regrowth and contact your hair surgeon for an evaluation too. Good luck.