Getting rid of ladders in a sweater

Hi all. I’m fairly new to this form. After completing a project last night, I realize I may need a bit of help. I am working on the flax sweater which I like because it is made in the round. I used 2 circular needles so it went quick. I have made socks this way and the ladders usually go away after a wash or 2. However, didn’t happen in this sweater. They are especially noticeable on the shoulders and the “seam” under the arms. Is there anything I can do to save my sweater? I wanted to give it to my little boy for a Christmas party that is coming up.

Thanks for the advice.

Usually these ladders do improve but it not, you might try adding an extra stitch to close up the ladder. You do this on the finished sweater.
See figure 2 here:

Thanks I may have to do try this. The sides of the sweater look light they might close, but the shoulders have a column of ribbing where you purl every other row. The sleeves turned out nice and the stitches all closed. So I need to see about adding a stitch to just part of the sweater as the sleeves were knit attached to the sweater, not on their own.