Probably no direct consequences. For starters, the MPs don't have as much say for NI as the MLAs do (in theory, if Stormont sat). And the 2017 MLA election already saw a similar result:
The election marked a significant shift in Northern Ireland's politics, being the first election since Ireland's partition in 1921 in which unionist parties did not win a majority of seats, and the first time that unionist and nationalist parties received equal representation in the Assembly (39 members between Sinn Féin and the SDLP, 39 members between the DUP, UUP, and TUV). The DUP's loss of seats also prevents it from unilaterally using the petition of concern mechanism, which the party had controversially used to block measures such as the introduction of same-sex marriage to Northern Ireland.
As far as Westminster goes, since Johnson now has a very comfortable Conservative majority, he's not likely to need the NI MPs support for anything in particular...
If you want some sort of significance for the NI MP elections... is that they confirm the 2017 MLA election, so we might be looking at a trend here for NI politics.
For the first time, unionism no longer has a majority at Westminster or Stormont - a statistic many would have believed unthinkable just a few years ago.
It might also lead to some reshuffling or elbowing in the DUP since, e.g. Nigel Dodds (DUP deputy leader) lost his MP seat. Actually this might be the biggest piece of news in these elections regarding NI:
His seat, which had previously always been held by a unionist, was won by Sinn Féin's John Finucane.
That came after the SDLP agreed not to run a candidate in the constituency for the first time.
Sinn Féin representatives do not take their seats in the House of Commons, where the party has always held a policy of abstentionism.
While it may not have been a great election for unionism, the Alliance Party became the third largest party in Northern Ireland, after the DUP and Sinn Féin.
Given the SDLP lost all three of its Westminster seats in 2017, winning back South Belfast and Foyle - both with massive majorities - makes them the comeback kids of this election.
Also of note however is that Sinn Féin was also punished at the ballot box (although less than the DUP), so this election isn't exactly a nationalist win:
Sinn Féin also felt voters’ wrath across Northern Ireland despite toppling the DUP’s deputy leader, Nigel Dodds, in Belfast North.
With Northern Ireland in the grip of a healthcare crisis, the election’s big winners were the moderate nationalist Social Democratic and Labour party (SDLP) and the non-aligned Alliance party, which prioritised the restoration of devolution over traditional tribal appeals.
Leo Varadkar, the Irish taoiseach, said the “tectonic” results showed there was no longer a unionist or nationalist majority in Northern Ireland – a trend reflected in other recent elections.
He discounted talk of momentum towards a united Ireland, saying the region’s parties should instead focus on a fresh round of talks, due to start on Monday, to restore the assembly, with prodding from Dublin and London.
... although Sinn Féin claims it is
Speaking after the party won seven seats, Sinn Fein leader Mary Lou McDonald said: “It is now impossible to ignore the growing demand for a referendum on Irish Unity and I want to reiterate Sinn Féin's call for the Irish government to establish an All-Ireland Forum on Irish Unity without delay."