So I have the 2015 "13 MacBook so I read some articles to update firmware by holding the power button so i tried to try it for fun but I misunderstood the article and I held the power button while my mac had completed 1/4 of booting process. So I accidentally force shutdown my mac while it was booting. So should I worry about some firmware error or some sort of software error which I can't notice?
Any forced shutdown can leave a file in a bad state. At boot, you would only corrupt a system file, so that's usually easy to reinstall the OS so I suppose if you care about user data - that's the best time to force a stop.
High Sierra supports internet recovery and bootable install media, so the options to reinstall are much better than the old days where you needed a CD or DVD to reinstall and it took a long time.