Networking: when to contact back

Hi guys,

I need some tips from networking pros.
I had an HR interview before August (I was told that they were not contacting me back until september due to vacation)

I was called to this interview due to a referal from a Senior Manager I cold-mailed through Linkedin. The question is, should I contact HR, send a message to the SM or neither, just wait a bit more to contact back?.

Thanks