Hi Hiatal surgery newbie,
Welcome to us Fellow Gerdie Troopers.
Yes it is very normal to experience pain when introducing advance diet to new surgical areas. Your surgery area is not yet fully healed. It does take some time to heal. Try more soft bland food for example , vanilla pudding , Sweet potatoes( just the orange part not the skins), Spinach , bananas. applesauce, oatmeal for example. Stay away from spicy hard cracker type foods for now. The meat I started with when I advanced my diet was chicken grounded with some gravy. You can read my Sweet Potatoe first time Tif hiatal thread as I kept a daily food diary to foods I advanced on what post op day and how I reacted to them.
Hope this helps and good luck for happy healing.