It's possible.
The built up fouling plays a part in how the bullet travels/exits the barrel and everything that happens from there.
When you clean it out you've changed that, so the point of impact may change.
As the fouling builds up through firing from a clean barrel to a more normal level it may wander a little before settling like Chronos said.
All that said though don't over analyse it and stress
It's possible, may happen a little, may not be noticeable. And the end of the day it's a Tikka for hunting and it will still be up to that task after cleaning, no worries.
If it's never been cleaned then it sure as s**t needs one. You'd be doing him a favour by extending the life of his rifle for him.