You can buy 'ant stations' which are small round boxes, to place near an ants' nest. They work for me, as I got fed up when the ants kept biting me as I knelt down weeding the beds. They're available at Garden Centres, DIY shops or even supermarkets.

if the nest is in a low spot you could just drown them bye overflowing the hose pipe to . or make a low spot bye digging down a bit .

oops sorry perhaps not in your lawn lol .