Never tell a soul ... honestly, even the most trustworthy of friends will either expect money from you, or blabber to others.
The best thing you can do is, meet with a financial advisor. Go to someone who knows what they're doing - someone who specifically mentions that they deal with lottery / inheritance amounts. If it takes time to find someone like that, then put the money on term deposit at the bank for six or 12 months. Don't put it in your everyday transaction account.
Hold off buying anything to begin with - sure, treat yourself with some new clothes or a night away somewhere - but be cautious about drawing attention to yourself.
