It is lovely. both your fabric choices and your points! I have trouble having my squares come out with points that crisp. I think you'll find that bias is the culprit on the puckering. As many have said above, starch - starch and starch.

You have done a very nice job! Love that block and your colors!!!

Accurate cutting helps a lot with the puckering as well as paying attention to the bias edges as was mentioned. I don't starch at all, just my preference, but it would help you get more accuracy in the cutting and the piecing at first. Have I said accuracy enough?? Accurate cutting, piecing and seam width will make all the difference in a quilt.

I think that you did a great job for your first attempt!

A hammer can be a good thing!

this is such a nice pattern and you are doing a beautiful job on it. I'll have to try one of them...keep up the good work..thanks for sharing

Very pretty block! I press all of my seams open. It helps in the bulk and I don't get creases in my seams. Also I press every seam after it's sewn.

I hate to admit at 80 I'm just learning all the different quilt blocks. Never really got into the big quilts. Most of the things I do are small so I can be sure to finish. I get bored very easy with things too large. This is a beauty though and I would love to make a table topper with it.
Looks like you did some very nice work. Hope to see the finished quilt sometime.

Are you sewing through the ¼-inch seam allowances? Don't. Unstitched SAs allow them to be moved/changed direction when pressing. Where four or more seams come together, press them in one direction and the seams will lay down like a flower. Pressing is an up and down motion, not sliding back and forth.

It's also better to reduce the stitch length when beginning or ending a stitching row. I drop the length to 1.5 for about ½-inch at both ends and increase to 2.5 in the center of the stitching row.

That said, your block looks great and appears square! Way to go...
Sandy Quilts

It is a very pretty block. If you are concerned about the puckering, how are you making the half square triangles? They are less likely to pucker if you make them by the method found in the link below. If you are joining two triangles together then there is more likelihood of them puckering along the biased edges.

http://youtu.be/k-nme6km8h8

I do this as well..love your block!