How to kill Purple Dead Nettle in my yard without harming my grass?

https://www.youtube.com/watch?v=nGvLgBP5cCw you may also want to check with your local Agricultural Agency

Water it a few hours before you try to pull it (with thick gloves), it helps. If you pull it when it is smaller it is a lot easier. If you find it blooming, take off the blooms before they can dry and spread the seeds and cause more plants. If the plants are already big with thick stems, I cut them off close to the ground and paint the cut with chemical spray for weeds. Painting them keeps it off the grass and other plants you want to keep and cutting them puts the chemical closer to the root system to work faster. I use the ones that are safe for the grass and only kills weeds and it works well for me. The biggest thing is to not let the plants go to seed to keep the numbers down. I fight them all the time, I have a neighbor that doesn't take care of any weeds in her yard, sometimes I sneak in there and cut them down and treat them.

Some info here: https://www.canr.msu.edu/news/scouting_for_weeds_henbit_and_purple_deadnettle