Should i wait for him?

I have known this guy for quite awhile and we would text each other everyday and he would flirt here and there telling me that i wa his type and he would always message my friends to ask them about what i like or to ask what i was doing when i don't reply. normally i would flirt back since we both know that we like each other, but the thing is that we are not dating yet. One day, he message me and said " Can we just be best friends?" and my friend showed a screenshot of him telling her that he likes me but because of some reasons we can only stay best friends for now and he said that the reason is very important and that he can't tell anyone and since that day onwards, he has been acting weird. Like he used to sound very happy but suddenly he's acting very cold towards me. My friends and his friends told me to wait for him and let him settle his problems. Should i listen to them and be more understanding and wait for him? ps. no one knows what's the reason