I just purchased a tangerine tree. It is approximately 2 feet tall... it has very small fruit starting to appear in the month of October. Should I be Worried about fruit coming in so late? What should I do?
Where have you got your tree now?
I would cut the fruit off to let the tree build it's strength over winter.
Citrus trees can flower and have fruit forming at the same time and at any time of year depending on where you are and how cold it is. Where are you and do you have frost free greenhouse or conservatory where you can keep it. It won't like to be in a warm, dry room.
I agree with Obelixx - that is the nature of Citrus - flowers, embryo fruit and mature fruit at the same time. Both my Lemon and Medica ( outside but sheltered in the SW UK ) are flowering whilst having small fruit. If you looked at a Citrus grove in southern Europe now, you would see exactly the same.
A cold GH or Conservatory is much the best bet once the frosty nights begin. Citrus don't make happy house plants - they aren't designed to be such whatever the GC.s try to tell us