Graffiti and social media posts has been identified as early indicators of dissatisfaction, but feedback is not causing the force significant concern, the Police Service of Northern Ireland (PSNI) said.
Assistant Chief Constable Mark McEwan said: "We are seeing signals, there are signal incidents that have happened, particularly in recent days.
"We are starting to see graffiti, we are picking up social media sentiment of a growing discontent, particularly within the Protestant/loyalist/unionist community. That has not manifested itself in any out workings at this point."
However, the force is preparing for a rise in demonstrations over trade disruptions once the lockdown restrictions ease.
The Northern Ireland protocol meant that a hard border was avoiding on the island of Ireland, with a regulatory border instead created in the Irish Sea between Northern Ireland and the rest of the United Kingdom.
Large suppliers and supermarkets have been given a three-month grace period until 31 March to adjust to the new regulations.
Mr McEwan warned that unless a solution is found by the end of the period, some goods may become more expensive in Northern Ireland, or even become unavailable.
Earlier this month, major UK supermarkets warned the government that “urgent intervention” is needed to prevent significant disruption to Northern Ireland food supplies, calling on them to agree to a long-term solution with the EU before the end of the grace period.
The senior police officer told the Northern Ireland Affairs Committee of MPs: "That will focus people's minds, I believe, in terms of how Northern Ireland looks and feels for certain members of our community."
He added: "If we get to the point where we don't have such stringent restrictions, where people are not as worried about the health crisis, we may see that manifest in the likes of protests, and we are prepared for that."
He said the force is monitoring the unionist community, though intelligence has not caused serious concern so far.
"Were we not in this current environment around the pandemic we would probably see a more visible outworking of that on the streets of Northern Ireland," he added.