People dont llike me?

i meet a person and after they wont even look at my face next day.most ppl are like that.if i see this person again should i avoid him too or talk to him?because he doesnt want to talk he tries to ignore me.dont tell me that he may be doing it mistakenly.my question is what to do how to behave or treat to him.if he says hi for example(coz i see hi everyday) should ay hi to him or just ignore?