I agree with the others; the issues will go away with washing, and I wouldn't worry about it.
Next time, if you want to avoid this altogether, I recommend:
(1) *heavily* starching the backing fabric before layering. I use a 1:1 solution of Sta-Flo liquid laundry starch and water, "paint" this on the fabric with a large wall painting brush, let sit for a couple of minutes to make sure the fabric fibers have absorbed as much starch as they can, toss in dryer, then iron with steam. This stabilizes the backing fabric so it has no chance of puckering while you sew. For me, it also helps to spray starch the top before layering. These two things *greatly* reduce the chance of puckers if you are crossing lines (as in cross-hatching).
(2) Spray baste. Spray basting adheres all areas of the fabric to the batting, unlike pinning -- which attaches the 3 layers only at points, usually about 4 inches apart. Glue basting probably has a similar effect to spray basting. When all of the layers are connected at all points, the fabric is not able to shift even slightly while you are machine quilting.