I've just started Invisalign, and my week 1 tray doesn't fit perfectly. what can I do? (Photo)

Thanks for posting the pictures. It looks like your tray are fitting pretty well. From your pictures I don't see any problems. Your teeth won't fit together with your aligners in place because they are covered with plastic. Don't try to force your teeth together or you may crack an aligner. If you have concerns I would contact your dentist.

First, ask your dentist what to do.  Sometimes when the tray doesn't seat all the way down you need to help it go down by chewing on chewies or something the can help seat it all the way down. As long as the trays are not bouncing when you close then that is a good sign.  If it feels like the tray is bouncing then it is not seated all the way down.  Your dentist will have to make the call on what to do.   

Great job with the photos! It would appear the aligners fit well, they just don't feel like it. Your teeth are not going to touch with the aligners in place. The bite with the aligners does feel different because of the contours of the aligner surfaces- they are not designed to chew.As your treatment progresses, you will become use to this. You likely have become aware that your bite without the aligners in place is different and will continue to feel different with each passing aligner.You should speak with your Invisalign provider about your concerns. All looks good so far.