Right now,it is a given that both titles are above 1 million, but it is possible that both passed that mark a good while ago. Back in april, Nintendo gave the quaterly reports on their earnings closing on march 31, there it was noted that the Switch, at that point, already had 12 million sellers that 8 being first parties titles and the 4 being thirds: http://gamrconnect.vgchartz.com/post.php?id=8787227
Those 4 third party titles were not revealed by Nintendo, but we already had a clear indication that 1 was Mario + Rabbids, since it was reported by Ubisoft long before, and another was Pokken Tournament, that was revealed shortly after. So it was left to wonder what the other two were, but everyone was certain Bomberman R was one of those because of that report: http://www.topesko.com/2018/03/super-bomberman-r-broke-one-million.html
We knew a few details also that excluded a few possibilities: Fire Emblem Warriors had just reached 1 million shipped combined on Switch and New 3DS, so that was not it. No digital only titles had reached that mark so Stardew Valley, Minecraft and Rocket League(That were still digital only back in the day) and Overcooked were also not it. And by recent reports, Puyo Puyo Tetris and Street Fighter II were also not in that mark. So by logic the other millions seller was either Fifa 18 or Skyrim,that according to Vgchartz were the ones closest to being million sellers.
HOWEVER looks like people misunderstood the report of Bomberman R selling above 1 million. That because Konami released today a report celebrating that the game JUST NOW became a million seller. And it was probably due to the launch of the game on PS4/ Xone/ Steam, so it is likely that is not even a million seller on Switch yet: http://www.nintendolife.com/news/2018/08/super_bomberman_r_hits_one_million_worldwide_sales_konami_celebrates_with_bungee_jump
The actual report was that in march the game was APPROACHING 1 million sales. So that leaves with the only two candidates left: Skyrim and Fifa 18, that probably both reach that mark long ago.