When you quilt, start in the middle and work your way out. Otherwise you'll get unwanted puckering. How did you baste it--with pins? spray baste? thread basting? If with pins, be sure to place each one about a hand width apart, and remove them carefully, don't hit them. (Very bad for machines--more than a broken needle, a little piece can get down in the machine and damage delicate part. Worst of all, a pin could break and fly into your eye. Or close to it. Ask me how I know. Glad I was wearing glasses!)
Have you quilted anything before? If not,I'd suggest making a practice sandwich with maybe a big four-patch on top so you can practice SITD. For my first quilt, I did a big X through each block and a wavy line through the sashing .Have fun!