I recently done an oil change on my Audi A4 Avant 1.9tdi. At the time I didn't have the tool to open the oil filter so i couldn't change it. I've bought the took and am going to put a new oil filter in (2 weeks later). My question is, do it need to change the oil again or is it ok to just change the oil filter? A mechanic said I have to change the oil also as it could be contaminated with debris from the old oil filter.
I would go ahead and change the filter.
I used to run a high quality & expensive oil for 20K and change the oil filter every 5k - the filters were so cheap in comparison - even quality ones.
When you change your oil, you never get all of the old out. There will be some left in the sump and on all the internal surfaces. Not changing the filter just means there will be a little more old oil left than normal.
Change the filter now as you suggested. If you want to you could change the oil and filter a week or so earlier next time.