If you change the lead status to anything other than the default "Lead" status, the sequence for this lead stops. No more emails will be sent to this lead.
Find the specific lead and open the Lead data, change the status "not interested" or anything else and click Save:
If you made a mistake, you could put the status back to "Lead" and this lead will be reintroduced to the sequence and continue from where it got interrupted by the status change.
If you want to delete this lead completely from your campaigns, this article may help: https://help.instantly.ai/en/articles/7895423-how-to-remove-a-lead-from-campaigns