Keep asking... Help if you have idea!!

So there iss a guy i used to like (i don't know why) but now i am absolutly not interested in him. We had a long history as we were almost together and after not speakin for a year. Now i was hapoy everything got back to normal and we are friends. But than he asked my friend if i am single and if it would be a good idea to hit on me? And that he don't understnds me why i am not interested in him... and now i don't know what to do... i don't want to be rude again (last time i tried to get rid of him like not speaking to him) but i don't want him to feel he has a chance, because he hasn't. And what shoulfld i do?? Advice??? I am quite affraid.😦😦