I've been in a little Instagram K-hole the last couple of days 是什麼意思

查看翻譯

K-hole is a rare (among normal civilised adult Britons) term derived from K as short for Ketamine, a dangerous drug misused for several purposes, including violent ones.

To be in a K-hole means to be briefly obsessed with a specific, narrow topic. I expect the speaker in your sentence is saying they have been using Instagram a lot in the recent past.