Is it possible to stop Invisalign treatment during the first two weeks?

If you are happy with how your teeth look you should be able to discontinue treatment. Since some movement did take place you might still need to have a retainer made to hold everything in place

Yes, it is possible to discontinue treatment at this time if you have decided you are happy with your teeth where they are now. It is normal to feel some discomfort, especially during the first 2-3 days after you start a new set of trays. I would encourage you to try to continue the treatment but totally understand if you feel the discomfort is not worth it. If you are not concerned with the refund, your doctor should understand. 

Yes I agree that sometimes a patient just wants one tooth corrected and some people think it is not worth it.My opinion is that the tooth may be unstable and could get worse; so there is merit in getting it corrected.Your symptoms of pain however are alarming and I would let your dentist have a look/ take a radiograph to make sure there is nothing untoward.If you still want to stop then that is fine if all agree.

As long as you are OK with not getting a refund, I see no reason why you should not be able to stop.  I don't understand why you would want to stop treatment though.  Good luck