Yes, having a pinch of saunf after meals is totally fine to beat that nasty acidity! Just don't start eating bowls of it like it's a main course lol. Moderation is key, dear!
Eating a tiny amount of fennel seeds as a mouth freshener or in food is generally safe. However, large therapeutic amounts or fennel oil should be avoided during pregnancy. It is always best to clarify with your doctor if you are unsure.
My saas always gave me a few fennel seeds to chew on whenever I felt bloated or nauseous. It really helped digest food naturally. Just keep it to a small teaspoon a day, as having too much is not recommended.
Whenever I had bad gas, I used to boil a few fennel seeds in water, strain it, and drink it warm. It's a very simple and working solution instead of taking acidity medicines. Just keep the quantity normal and it's perfectly safe.