You did a wonderful job for a first quilt. I think when it is washed you won't see any puckers. There are no mistakes in quilting - only design opportunities. When I used to have to use the floor I used masking tape to tape the back down, then put the batting on, being careful to smooth it well and tape if necessary, then put the top down, smooth, tape then pin with tons of pins. I have heard other use T pins to pin it to the carpet. When pinning, don't try to close the pins with just your fingers - use a spoon or something to help.