Either a hydraulic lifter needs replacing, or the cam or balance belt
tensioner(s). You need to get this diagnosed ASAP. If it a lifter, it can be
taken out, cleaned or replaced without taking the cams out: just use a big
bar to depress the valve spring. Try reving to 3000 rpm for 30 seconds, and
see if the noise goes away.

If the belts or tensioners are loose, you risk jumping a tooth or stripping
the cam belt. When this happens, you bend the inlet valves, requiring a head
rebuild and big expense, in the order of $1000. If the belts have not been
changed for 60K km or you don't know when this was done, get it done.

The noise may also be the water pump.

Approximate costs are

belts    C$60
water pump    C$35
labour 2-3 hours  $120

If the tensioner bearings need replacing, add C$100 or so.