Is it okay that my donor area looks thinner now? (Photos)

Your donor area will always look "thinner" proportionate to the number of hairs taken out after a FUE harvesting surgery.  The hairs will NOT grow back from the donor area (where it was taken).  If it all goes to plan the donor hairs will grow in the area it was transplanted.

You did not mention how many grafts you had done but I suspect there is some element of over harvesting.Only time will tell-if the donor area still looks thin in another 6-8 months than likely this was due to aggressive harvesting.

Hi, 
It is normal to see a bit of thinning. 
Because almost 1/5 of hair follicles are harvested and even 1/4 may fall off because of the trauma of the harvesting.
A few PRP injections and taking care of your diet and vitamin-ion supplements would help you. After your hair gets longer, it would be almost invisible.
Best wishes,

Thinning of the FUE donor area is due to several factors-  the number of grafts harvested, the size of the punch, and the original density being the most important.  It is imperative that not too many hairs be harvested from the donor area -  that is why most of my FUE cases do not involve more than 2400 or so grafts in one procedure.You can consider SMP for the scarring if it does not improve.

It is too early to say for sure at only 3 months. It is possible that some of the areas were over-harvested. But it just may be that you take a little longer to heal and grow back the other hair in the donor area. Give it a few more months and if it is still not filling in, SMP is a solution to blend it all in again. 

This is what can happen after an FUE. IF it bothers you, then Scalp Micropigmentation can solve it as these hairs will not grow back