Rules to live by:
1. The seam ripper is your best friend.
2. Tear it out and re-measure your pieces. If they are exactly what they are supposed to be, re-sew. If they are not and you have extra fabric, just recut those pieces that you need to.
3. Take painters tape for masking tape and mark off on top of your needle plate 1/4 inch line. Place the tape 1/4 inch from the needle. Use this line as your guide.
4. Sew the block again. Measure the block.
You should be good to go.
PS. There are no quilt police on here. A lot of varied opinions of different things that work for different people. Try several different things and keep what works for you. But good habits are best started at the beginning. If you are consistent now, later on you'll do it automatically. And many patterns require that you be exact on that 1/4 inch.
Don't give up. I have a seam ripper in my sewing machine, my thread cabinet, on top of my bookcase, and in my purse. Plus a couple extras that I've picked up just in case I can't find one. LOL