I ran into my ex after 2 years apart. My date & I randomly saw him at a liquor store. Then my ex texted me?

Sounds like he was drunk and got jealous when he saw you with someone else. I wouldn't worry about it too much, unless it continues. If he keeps doing it, you can't just ignore him. You have to tell him to stop and leave you alone. If he still continues it after that, it's called harassment. Block his number if you have to.