Remove seasoning packed from beans and set aside. If desired, soak beans for a couple of hours.
Place ham bone and leftover ham in Instant Pot. Add drained beans and 8 cups of chicken stock. Place lid on pot and set to Manual for 50 minutes, then do a quick pressure release. Remove ham bone from pot and remove as much ham as possible from the bone. Return ham to the pot and discard bone.
Add the tomatoes, onion, garlic, lemon juice, and seasoning packet to the pot and stir. Return lid to pot and set to Manual for 10 minutes. Do a quick pressure release, stir, and serve.