Answer:
The answer is yes there was a contradiction.
Step-by-step explanation:
Balfour made that statement under pressure from the Zionist movement, seeking to establish a Jewish homeland in what was then Palestine, and the need for finance for the British war effort from the international banking community largely controlled by Jewish families. Indeed the Declaration was sent to The Rothschild banking family.
We have to understand what the British perception would have been at the time. Britain still had the largest empire in the world. She was fighting Turkey, an ally of Germany so was helping local Arabs as Turkey controlled Palestine.
They were also making commitments to the Jewish population in return for financial support. This seems strange if not ludicrous now, making the same promises of land to two competing groups, but the British at the time would have, from their imperial perspective, not seen this as a problem.
When World War 1 ended Palestine was given to Britain as a 50 year mandated territory. Almost immediately, the Palestinians demanded what they had been promised as did the Jewish population, both in Palestine and throughout the world. The situation was further compounded by the coming to power of Hitler and the pressures that caused on the Jewish community.
In 1948 the UK handed Palestine over to the UN who partitioned it between Palestinians and Jews, causing the first Arab-Israeli war. Much of this conflict, which is still continuing to this day, stems from British foreign policy and The Balfour Declaration in 1917.