Poncho neckline sagging

Hi to everyone. I am a newbie also to knitting, I have made a poncho from 4 different knitted squares, I have sewn them all together, knitted the neckband which is garter stitch made up of 5 sts across on 4mm needles. I have sewn this to the poncho but after trying it on the neck looks sloppy, I am unsure of best way to rectify without unpicking the neckband, the neckband just looks like it needs to be tighter (or not so wide) it is exactly as the pattern says, the squares are made of Moss stitch, garter stitch, 2 x 2 rib stitch and ridge stitch. Does anyone have any help for making it a bit tighter. Thanks in advance Anne

Welcome to KnittingHelp!
Probably the best thing to do is take the neckband off the poncho. You can the pin it back using only as much of the band as you need to make it look neater. Once you know that, take out the extra knit rows and bind off again.
When you pin it in as a shorter piece you will also be able to tell if the width is a problem in itself. If so then you need to re-knit the band with fewer sts and for a shorter length.
What pattern are you following? Can you copy and paste the URL into a post?

Knowing your pattern would be helpful. Is it online so you can link to it?

Thank you for your reply, this is the pattern along with wool I used, I needed to adapt the pattern to the wool I used, e.g. more stitches as wool not as thick and smaller needles, I started this mid 2016 to give myself a project due to having a hip replacement. All I needed to do to complete was a couple more squares & neckband.
I have just realised that I should have put more stitches on for the neckband, I have not allowed for the different sized wool & needles, I was getting excited that I had nearly completed the project & wanted to wear it. I will unpick & redo, would a different stitch make it a bit firmer maybe, I am unsure if I am a loose knitter, thank you again for replying, any suggestions are greatly appreciated.

Thank you for your reply, please see above post

Nice looking poncho! I hope that the hip replacement went well and that the knitting helped with your recovery.

Garter stitch in that direction is going to be very stretchy. I wonder if a k1p1 or k2p2 rib might be less stretchy? The neck opening looks like there’s plenty of room but make sure the neckband doesn’t narrow it too much.

In the photo it looks like the ends of the neckband are crossed at the center front. That would make them lie flat. If you like that look you could make the band in two pieces and overlap at both the front and back.
We’d love to see a photo when you finish.

Thank you, the knitting helped recovery,
I thought about k1p1 or k2p2, I have unpicked it & redoing but knitting more tightly, along with 5 extra stitches.

It does cross over & is in2 pieces, thank you for your help, I will post a photo when completed.