I just had two extractions and then bone graft. I feel pieces of tooth embedded in my gums

The odds are that this is bone graft material and not tooth structure.  It is normal for small granules of bone to come out  for a week or two after your surgery.  I would not be overly concerned.  

It sounds like its the remnants of the bone graft.  You should have your dentist check it just to be on the safe side.

It's very difficult to know without actually seeing your mouth, however it is likely that you're feeling some of the bone grafting material. Sometimes the texture can be rough or bumpy and may feel similar to a piece of tooth. It is important to have it checked out, and I would recommend having the dentist evaluate the area to ensure that it is healing normally. 

It is not uncommon for granules of graft material to come to the surface after the surgery.  It is rather uncommon for fragments of tooth to surface the same way.  Have your doctor evaluate the site. 

It's hard to say if it's a piece of root coming to the top and body expelling it or if it's granular bone particles you are feeling. If you showed some photos it might be easier to tell. However, it is not unusual to have some bits of bone particles expressing themselves out of the gum on a bone graft SO LONG AS the site is not opened up and the entire bone graft is coming out. See your surgeon to assess. 

There are 2 types of bone (cortical or cancellous) and can be in different particle sizes (.25 mm, .5 mm, 1.0 mm).  We hope most particles stay put and become part of the body, but sometimes some of them escape.  It usually is no big deal and nothing to worry about.  See your dentist to be sure.

You are most likely seeing and feeling the bone graft material. Have your surgeon take a look. It usually isn't serious at all.