I get some small ones in my lawn from time to time I just ignore them and they go away.

You can't, Guest - they're just the fruiting bodies of strands called mycelium which are already present in the lawn. They'll disappear on their own, but you can twist them off every day and dispose of them if you don't like them until they do.

If they are of an edible variety, you are lucky provided you have enough of it. Otherwise nothing to worry about as they dry up in no time; some mushrooms of course are poisonous and some could give out foul smells too. But the real reason for them to come up maybe because there is something rotting under the soil like perhaps pieces of old wood? Guesswork mostly.