- First, rule out the cheapest option: get the car's PCV valve changed. Go to any japanese/used parts market, get a PCV valve for your Vitz (in local language they call it blow vaaal).
Observe smoke and oil consumption. If stopped, you're good to go in cheap price. Do it first!
- Other reason could be internal engine related, like bad piston rings.
No worries and you can continue to run it like now.. just keep a strict watch on oil level, check after every 1,000KM and top up as needed.
Of course, to completely remove this issue will require engine replacement OR rebuild (if cause is bad piston rings).. but, no need to spend thousands n thousands to stop this issue... or you can, when engine goes complete dead. Who knows when, it might run a really long time just fine.