and now I have no idea what to do 
We haven't spoke to each other since last night as we've both been working today but I'm not sure if I should contact him first or should I wait for him to contact me?
I don't know what he thinks about it and whether he thinks it meant something or it was just a casual one night stand. I'm not even sure I know tbh
Should I mention this to him or just forget it ever happened and continue on as normal?