A stitch came out and now there's a hole. will i get dry socket?

Not likely: The stitch coming out will not cause a dry socket if there is a healthy clot in the extraction site. It may appear that there isn't but the extraction site is as long as tooth that was in it and the primary area that dry socket occurs is more than 3 mm below the surface of the gum. The hole you see is probably very shallow. Follow your post operative instructions and consult your dentist

Not necessarily : Depending on how soon after the surgery the suture came out you might want to contact the treating doctor to see how he wants to address it. Hope this helps.