I had a blood test done & results: AKI warning grade 1. Creatinine 107 umol/L. Estimated GFR 55 'consistent with CKD stage 3A. What does this mean?

Kidney dysfunction. The kidney filters blood in order to draw out waste/urine. Your GFR (glomerular filtration rate) is a bit low, but not urgently low. Whether this is an acute (aki) or chronic (ckd) problem depends more upon you medical history and the original indication for obtaining this test. The physician who ordered it is better equipped to make an interpretation beyond this level.