Dated my neighbor and it didn't work out, how to act when i see him?

dated my neighbor right next door (we share a wall ). At the time, his mom who comes almost every day said hi and he was saying hi. well it turned out he is a huge jerk and lied and i pretty much hate him for breaking my heart. additionally, i wound up teling on him to the landlady for his weed.(this was not something that was happening when i dated but after we broke up his friend moved in hte weed smelled so bad it was coming through the wal and i have a little girl ). i treid going to him about it but he was a total dick and wouldn't stop. i waited like two months for it to stop before going (i really didnt want to cause of the history between us ). so now his mom was saying hi and i pretty much snubbed her. i dont feel comfortable abou ttalking i get a huge anxiety attack whenever i go outside and him and his mom are out there. today i seen him he was right there and looked right at me. i didnt even look at him bu tonly saw him otu of the coerner of my eye. i didnt look at him or do nothing i just llooked ahead of myself at the door. is this proper etiquette ?? i maybe should be friendly since were nieghbors, but i just dont feel like it. i hate him and its a bonus i dont say anything shitty. i jus worry he will think im being immature like im not over him yet. i sure dont want to give him that satisfaction... how should i act if i see them just pretend theyre not there ?