Oxtoby had spoken about the challenge of facing a side who had qualified for Euro 2025 as Northern Ireland look to earn promotion to League A for the first time.
Northern Ireland started brightly as Lauren Wade's dangerous cross was plucked out of the air by goalkeeper Kinga Szwmik, but from there the hosts dominated.
Poland had the ball in the back of the net in the 10th minute as Nadia Krezyman tucked home, but the goal was ruled out as Kamczyk had crashed into Burns before the ball reached the winger at the back post.
Bristol City goalkeeper Burns was called into action to tip Natalia Padilla's effort around the post, and Pajor headed into the side-netting as the hosts continued to threaten.
Northern Ireland's resolve was broken with a quickfire double from Poland.
The opener came after a long ball over the top of the Northern Ireland defence by Wos, and Kamczyk held of McKenna and lobbed Burns, who was stranded on her six-yard line.
Things went from bad to worse for the visitors three minutes later when Pajor spun away from Rafferty, raced into the area and squared the ball for Achcinska, who took a touch and slotted into the bottom corner off the post.
Barcelona forward Pajor was at the heart of Poland's good play, and she had two efforts well blocked by Rafferty to keep the margin to two goals at the break.
The second half continued in a similar vein to the first as Achcinska fired well wide before Burns was forced into a good save to deny Pajor.
Oxtoby handed a debut to Kascie Weir with 16 minutes remaining and the 18-year-old striker showed some neat touches in her cameo off the bench, but there was almost trouble at the other end as Burns pulled off a superb save to poke Natalia Padilla's effort away with her toe.
While NI looked a more settled and solid side in the second half, they struggled to create any clear-cut chances to get back into the game and were left to rue the three first-half minutes when Poland got the decisive goals.