I’ve made this post to document my experience that may help others.
I had carried out a full system update with pacman -Syu in the background and i had been using adb with a device prior although i don’t believe it was related to my issue.
Whilst it was updating it moved on to upgrading packages, unfortunately it seemed to hang while updating Virtualbox, it was stuck upgrading this packages for about 15 minutes, i assumed there must have been a problem, not acknowledging that it had also yet to update the kernel i used ctrl+c interrupt signal and then rebooted. (problems snowball from this point) 
(Proper school boy error i know, Dont remind me lol)
At this point it would not boot past the boot loader boot menu as when i selected the first boot option it gave an error message that the kernel was not present or unable to find kernel image(along them lines). I checked the grub boot script using e command and it was showing a boot script, so i chrooted in to the filesystem
https://wiki.archlinux.org/title/Chroot
Using a bootable USB archlinux installation i continued with pacman -Syu to finish the update of the uncompleted packages to be upgraded, then used grub-mkconfig -o /boot/grub/grub.cfg to create a new boot script, then i found out that manjaro has the update-grub command which i could have used instead lol (never mind). All jokes aside now my grub script did not even show any instructions to boot (from the boot loader boot menu e command) 
. Long story short i noticed the kernel image in /boot had a .kver extension and /etc/mkinitcpio.d/ directory did not show my kernel version although it did show 2 others that i was running before the current one.
My suspicions was that it was a kernel issue anyway as i was expecting to see vmlinuz on its own in /boot not with that extension that i haven’t seen before plus at least an initramfs.img image file but neither was present, only the one with .kver extension, as i was originally trying to boot from grub command line but couldn’t find the files.
After reading a few posts i figured it must be the kernel that had not completed installing/upgrading after reading this
along with additional commands that would otherwise have been executed when carrying out a kernel upgrade
I ran mhwd-kernel -i linux515 whilst i was chrooted in the filesystem all outputted an error message advising me “no targets specified” after it refreshed the pacman database, so i tried all the different versions until linux66 which did seem to work and asked me to confirm installation, and rebooted.
I could now see a populated boot script using grub e command from Manjaro grub boot menu with the kernel version with linux66 option showing to boot from. Failing this i would have tried installing a new kernel via pacman.
following this link also helped
Please be aware my boot menu was already showing as i made it that way some time back before my issue, your’s may not be showing and if this is the case this is how you access yours to see if there is a boot script present assuming your grub script is being shown and there are the kernel and initramfs images present in /boot unlike mine was. after you have successfully chrooted in to your file system open it with your favorite text editor (i use vim but if your not familiar you can use nano which should be installed) open the grub file using “vim” or “nano /etc/default/grub” command. You will see a list of configuration options but at the top possibly the 4th line or whichever line is on your file that reads GRUB_TIMEOUT_STYLE= this will most likely read “hidden”, some times it is not present if not just add it and include or change it to menu as in GRUB_TIMEOUT_STYLE=“menu” with the double quotes then save the file vim=:wq(write and quit) nano=ctrl+o(write) then hit enter, now enter update-grub and after its completed enter the reboot command and it should now show you the Manjaro’s grub boot menu providing there is a kernel and initramfs image present. If you have exactly that same symptom as mine you may or may not be able to get the boot menu to show depending if update-grub is unable to complete correctly. You will have to try it and see if it works, if not you best bet will be to carry out all repairs through chroot.
Further information about using the grub command line can be found here if you don’t already know how to use it
https://wiki.archlinux.org/title/GRUB
I hope this helps someone having a similar issue, i spent a fair few hours(may be half a day lol) investigating my issue because i did not want to just reinstall everything.
mod. edit: moved to correct section