You have to be slightly careful with what you out on your CV. Not including a job you had done in the past is not that serious and many people leave out certain short-term jobs as they would not want to or even be expected to include every job they have held. So that in itself is not a problem. What would be an issue is if you make a statement which is untrue. So if you go on to say you have no experience in the sector, that would actually be a lie. So if you had just left the jib out and left it at that, making no other statements, that is not really an issue, but going on to then say you have had no experience in the sector would be making a misleading or false statement so avoid that if possible.
In terms of how it can affect a current job – as a starting point if you have less than 2 years service anywhere you are not protected against unfair dismissal. So in that period they can dismiss you for more or less any reason, including because of this, even if it has no impact on your current job/performance.
After 2 years have passed you get more protection and then they could only potentially dismiss you for misconduct, such as lying on your application form or CV. As mentioned, not including the job is not a big issue, just do not make other incriminating statements at the same time as these could amount to misconduct which they cold potentially use to discipline or even dismiss later on.
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