In reading around the state news media Kyiv Independent (Ukr) and Tass(RU), and an article quoting NATO, I get the impression Russia is worried some of its drones may have crossed into Poland, but isn't sure and doesn't know why they would be there. The Ruskies may be wondering if Ukr. is able to 'conscript' Russian drones - which would make them lose confidence in their drone attacks on Ukr if theirs can be turned against them.
Putin may be worried their guys made a mistake for which Putin must account. Putin says he will consult with Polish minister - it's like he's not sure what crossed into Poland, and where.. It's as if Putin doesn't have enough information and is stalling while trying to find out more, and doesn't want to deny if they turn out to be his.
NATO and Ukr are in predictable outrage, but I don't think Putin has any reason to do this to Poland, unless he was spying and his drones were brought down. But I think Russia uses satellites for that.
Putin's Ministry of Defense says they had no plans for that location and notes the range of the drones is 700km - which may be they are saying they wouldn't plan a distant attack on Poland without the capacity for the drones to leave the area? I dunnoo
Kyiv Independent says it was 19 drones in the 'largest attack on a NATO member since the start of the war.'
NATO warns Russia:
TASS.RU
https://tass.com/politics/2015063