I believe we will need a little bit more information.
A knocking sound usually refers to a rod or crankshaft knock. Not a sound you want to hear on a new tractor.
Ticking type sound or other type noises can be any number of things.
Is the sound present as long as the engine is running?
Does it change with RPM increase?
Is it only when driving?
Is the temperature gauge in the normal range?
A video of the sound can be helpful as well, but if it is that prominent then going back to the dealer is about the best plan you could come up with.